run yamato tests on PRs that target v2-staging (#5026)

* run yamato tests on PRs that target v2-staging

* remove comments

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

     {% if platform.name == "linux" %}
     expression: |
       (pull_request.target eq "main" OR
+       pull_request.target eq "v2-staging" OR
       pull_request.target match "release.+") AND
       NOT pull_request.draft AND
       (pull_request.changes.any match "com.unity.ml-agents/**" OR

.yamato/compressed-sensor-test.yml

     {% if editor.extra_test == "sensor" %}
     expression: |
       (pull_request.target eq "main" OR
+       pull_request.target eq "v2-staging" OR
       pull_request.target match "release.+") AND
       NOT pull_request.draft AND
       (pull_request.changes.any match "com.unity.ml-agents/**" OR

.yamato/gym-interface-test.yml

     {% if editor.extra_test == "gym" %}
     expression: |
       (pull_request.target eq "main" OR
+       pull_request.target eq "v2-staging" OR
       pull_request.target match "release.+") AND
       NOT pull_request.draft AND
       (pull_request.changes.any match "com.unity.ml-agents/**" OR

.yamato/protobuf-generation-test.yml

     cancel_old_ci: true
     expression: |
       (pull_request.target eq "main" OR
+       pull_request.target eq "v2-staging" OR
       pull_request.target match "release.+") AND
       NOT pull_request.draft AND
       (pull_request.changes.any match "protobuf-definitions/**" OR

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

     {% if editor.extra_test == "llapi" %}
     expression: |
       (pull_request.target eq "main" OR
+       pull_request.target eq "v2-staging" OR
       pull_request.target match "release.+") AND
       NOT pull_request.draft AND
       (pull_request.changes.any match "com.unity.ml-agents/**" OR

.yamato/standalone-build-test.yml

     cancel_old_ci: true
     expression: |
       (pull_request.target eq "main" OR
+       pull_request.target eq "v2-staging" OR
       pull_request.target match "release.+") AND
       NOT pull_request.draft AND
       (pull_request.changes.any match "com.unity.ml-agents/**" OR

.yamato/training-int-tests.yml

     cancel_old_ci: true
     expression: |
       (pull_request.target eq "main" OR
+       pull_request.target eq "v2-staging" OR
       pull_request.target match "release.+") AND
       NOT pull_request.draft AND
       (pull_request.changes.any match "com.unity.ml-agents/**" OR