update tests to run on 2019.4 (#4451)

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

 test_editors:
-  - version: 2019.3
+  - version: 2019.4
+  - version: 2020.2
 ---
 {% for editor in test_editors %}
 Run_Mac_Perfomance_Tests{{ editor.version }}:

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

   - version: 2018.4
     # 2018.4 doesn't support code-coverage
     enableCodeCoverage: !!bool false
-  - version: 2019.3
+  - version: 2019.4
     enableCodeCoverage: !!bool true
   - version: 2020.1
     enableCodeCoverage: !!bool true

.yamato/gym-interface-test.yml

 test_editors:
-  - version: 2019.3
+  - version: 2019.4
 ---
 {% for editor in test_editors %}
 test_gym_interface_{{ editor.version }}:

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

 test_editors:
-  - version: 2019.3
+  - version: 2019.4
 ---
 {% for editor in test_editors %}
 test_mac_ll_api_{{ editor.version }}:

.yamato/training-int-tests.yml

 test_editors:
   - version: 2018.4
-  - version: 2019.3
+  - version: 2019.4
+  - version: 2020.1
 ---
 {% for editor in test_editors %}
 test_mac_training_int_{{ editor.version }}: