Switching to newer 2019.4

.yamato/environments.yml

 upmci_registry: https://artifactory.prd.cds.internal.unity3d.com/artifactory/api/npm/upm-npm
 
 coverage_editors:
-  - version: 2019.4.6f1
+  - version: 2019.4.8f1
-  - version: 2019.4.6f1
+  - version: 2019.4.8f1
-  - version: 2019.4.6f1
+  - version: 2019.4.8f1
   - version: 2020.1.3f1
   - version: 2020.2.0a21