Work CI-CD

- Add retry parameter to nuget restore AZDO task (was failing randomly and a retry fixes it).
- Remove github action for PR checks (isn't useful because POC solutions are always one version behind).

***NO_CI***

Author: josesimoes

.github/workflows/pr-checks.yml

@@ -119,13 +119,15 @@ jobs:
 
   - task: NuGetCommand@2
     displayName: NuGet restore Test Adapter
+    retryCountOnTaskFailure: 2
     inputs:
       restoreSolution: 'nanoFramework.TestAdapter.sln'
       feedsToUse: config
       nugetConfigPath: 'NuGet.config'
 
   - task: NuGetCommand@2
     displayName: NuGet restore Test Framework
+    retryCountOnTaskFailure: 2
     inputs:
       restoreSolution: 'nanoFramework.TestFramework.sln'
       feedsToUse: config