update master to main, remove pylint check (#5031)

.github/workflows/pre-commit.yml

 on:
   pull_request:
   push:
-    branches: [master]
+    branches: [release_2_verified]
 
 jobs:
   pre-commit:

.github/workflows/pytest.yml

     - 'test_constraints*.txt'
     - 'test_requirements.txt'
   push:
-    branches: [master]
+    branches: [release_2_verified]
 
 jobs:
   pytest:

.pre-commit-config.yaml

     hooks:
     -   id: python-check-mock-methods
 
--   repo: https://github.com/pre-commit/mirrors-pylint
-    rev: v2.4.4
-    hooks:
-    -   id: pylint
-        exclude: >
-            (?x)^(
-                .*_pb2.py|
-                .*_pb2_grpc.py|
-                .*/tests/.*
-            )$
-        args: [--score=n]
-
 - repo: https://github.com/mattlqx/pre-commit-search-and-replace
   rev: v1.0.3
   hooks:

.yamato/com.unity.ml-agents-test.yml

   triggers:
     cancel_old_ci: true
     recurring:
-      - branch: master
+      - branch: main
         frequency: daily
 
 {% for editor in test_editors %}

.yamato/gym-interface-test.yml

   triggers:
     cancel_old_ci: true
     expression: |
-      (pull_request.target eq "master" OR
+      (pull_request.target eq "main" OR
       pull_request.target match "release.+") AND
       NOT pull_request.draft AND
       (pull_request.changes.any match "com.unity.ml-agents/**" OR

.yamato/python-ll-api-test.yml

   triggers:
     cancel_old_ci: true
     expression: |
-      (pull_request.target eq "master" OR
+      (pull_request.target eq "main" OR
       pull_request.target match "release.+") AND
       NOT pull_request.draft AND
       (pull_request.changes.any match "com.unity.ml-agents/**" OR

README.md

 [here](https://github.com/Unity-Technologies/ml-agents/tree/release_2_verified_docs/docs/Readme.md)
 to get started with the latest release of ML-Agents.**
 
-The table below lists all our releases, including our `master` branch which is
+The table below lists all our releases, including our `main` branch which is
 under active development and may be unstable. A few helpful guidelines:
 - The [Versioning page](docs/Versioning.md) overviews how we manage our GitHub
   releases and the versioning process for each of the ML-Agents components.
 
 | **Version** | **Release Date** | **Source** | **Documentation** | **Download** |
 |:-------:|:------:|:-------------:|:-------:|:------------:|
-| **master (unstable)** | -- | [source](https://github.com/Unity-Technologies/ml-agents/tree/master) | [docs](https://github.com/Unity-Technologies/ml-agents/tree/master/docs/Readme.md) | [download](https://github.com/Unity-Technologies/ml-agents/archive/master.zip) |
+| **main (unstable)** | -- | [source](https://github.com/Unity-Technologies/ml-agents/tree/main) | [docs](https://github.com/Unity-Technologies/ml-agents/tree/main/docs/Readme.md) | [download](https://github.com/Unity-Technologies/ml-agents/archive/main.zip) |
 | **Release 2** | **May 19, 2020** | **[source](https://github.com/Unity-Technologies/ml-agents/tree/release_2)** | **[docs](https://github.com/Unity-Technologies/ml-agents/tree/release_2/docs/Readme.md)** | **[download](https://github.com/Unity-Technologies/ml-agents/archive/release_2.zip)** |
 | **Release 1** | April 30, 2020 | [source](https://github.com/Unity-Technologies/ml-agents/tree/release_1) | [docs](https://github.com/Unity-Technologies/ml-agents/tree/release_1/docs/Readme.md) | [download](https://github.com/Unity-Technologies/ml-agents/archive/release_1.zip) |
 | **0.15.1** | March 30, 2020 | [source](https://github.com/Unity-Technologies/ml-agents/tree/0.15.1) | [docs](https://github.com/Unity-Technologies/ml-agents/tree/0.15.1/docs/Readme.md) | [download](https://github.com/Unity-Technologies/ml-agents/archive/0.15.1.zip) |

com.unity.ml-agents/CHANGELOG.md

   - Introduced the `SideChannelManager` to register, unregister and access side
     channels. (#3807)
   - `Academy.FloatProperties` was replaced by `Academy.EnvironmentParameters`.
-    See the [Migration Guide](https://github.com/Unity-Technologies/ml-agents/blob/master/docs/Migrating.md)
+    See the [Migration Guide](https://github.com/Unity-Technologies/ml-agents/blob/main/docs/Migrating.md)
     for more details on upgrading. (#3807)
   - `SideChannel.OnMessageReceived` is now a protected method (was public)
   - SideChannel IncomingMessages methods now take an optional default argument,
   `--load`. (#3705)
 - The Jupyter notebooks have been removed from the repository. (#3704)
 - The multi-agent gym option was removed from the gym wrapper. For multi-agent
-  scenarios, use the [Low Level Python API](https://github.com/Unity-Technologies/ml-agents/blob/master/docs/Python-API.md). (#3681)
+  scenarios, use the [Low Level Python API](https://github.com/Unity-Technologies/ml-agents/blob/main/docs/Python-API.md). (#3681)
-  [Low Level Python API](https://github.com/Unity-Technologies/ml-agents/blob/master/docs/Python-API.md)
+  [Low Level Python API](https://github.com/Unity-Technologies/ml-agents/blob/main/docs/Python-API.md)
   documentation for more information. If you use `mlagents-learn` for training, this should be a
   transparent change. (#3681)
 - Added ability to start training (initialize model weights) from a previous run

com.unity.ml-agents/CONTRIBUTING.md

 ## Communication
 
 First, please read through our
-[code of conduct](https://github.com/Unity-Technologies/ml-agents/blob/master/CODE_OF_CONDUCT.md),
+[code of conduct](https://github.com/Unity-Technologies/ml-agents/blob/main/CODE_OF_CONDUCT.md),
 as we expect all our contributors to follow it.
 
 Second, before starting on a project that you intend to contribute to the
 
 ## Git Branches
 
-The master branch corresponds to the most recent version of the project. Note
+The `main` branch corresponds to the most recent version of the project. Note
 that this may be newer that the
 [latest release](https://github.com/Unity-Technologies/ml-agents/releases/tag/latest_release).
 

docs/Installation-Anaconda-Windows.md

 the ml-agents Conda environment by typing `activate ml-agents`)_:
 
 ```sh
-git clone --branch release_1 https://github.com/Unity-Technologies/ml-agents.git
+git clone --branch release_2 https://github.com/Unity-Technologies/ml-agents.git
-The `--branch release_1` option will switch to the tag of the latest stable
-release. Omitting that will get the `master` branch which is potentially
+The `--branch release_2` option will switch to the tag of the latest stable
+release. Omitting that will get the `main` branch which is potentially
 unstable.
 
 If you don't want to use Git, you can find download links on the

docs/Installation.md

 of our tutorials / guides assume you have access to our example environments).
 
 ```sh
-git clone --branch release_1 https://github.com/Unity-Technologies/ml-agents.git
+git clone --branch release_2 https://github.com/Unity-Technologies/ml-agents.git
-The `--branch release_1` option will switch to the tag of the latest stable
-release. Omitting that will get the `master` branch which is potentially
+The `--branch release_2` option will switch to the tag of the latest stable
+release. Omitting that will get the `main` branch which is potentially
 unstable.
 
 #### Advanced: Local Installation for Development
-back, make sure to clone the `master` branch (by omitting `--branch release_1`
+back, make sure to clone the `main` branch (by omitting `--branch release_2`
 from the command above). See our
 [Contributions Guidelines](../com.unity.ml-agents/CONTRIBUTING.md) for more
 information on contributing to the ML-Agents Toolkit.

utils/make_readme_table.py

 MAX_DAYS = 150  # do not print releases older than this many days
 sorted_versions = sorted(versions, key=lambda x: x.loose_version, reverse=True)
 
-print(table_line("master (unstable)", "master", "--"))
+print(table_line("main (unstable)", "main", "--"))
 highlight = True  # whether to bold the line or not
 for version_info in sorted_versions:
     if version_info.elapsed_days <= MAX_DAYS: