Attempt moving to newer unity version

.yamato/environments.yml

 # sticking to 2019.4.6f1 for testing for now because Linux Editor fails to open PerceptionHDRP on 2019.4.8f1
 # see https://fogbugz.unity3d.com/default.asp?1273518_d68j5lb6eucglb84
 coverage_editors:
-  - version: 2019.4.18f1
+#   - version: 2019.4.18f1
+  - version: 2020.3.15f2
-  - version: 2019.4.18f1
-#  - version: 2020.1.15f1
+#   - version: 2019.4.18f1
+  - version: 2020.3.15f2
-  - version: 2019.4.18f1
-#  - version: 2020.1.3f1
+#   - version: 2019.4.18f1
+  - version: 2020.3.15f2
-  - version: 2019.4.18f1
-#  - version: 2020.1.15f1
-#  - version: 2020.2.0a21
+#  - version: 2019.4.18f1
+  - version: 2020.3.15f2
 
 publish_platforms:
   - name: win