use latest MacOS image available for Android PR (#3704)

.ado/azure-pipelines.yml

@@ -39,7 +39,7 @@ jobs:
   - job: AndroidPR
     displayName: Android PR
     pool:
-      vmImage: 'macos-11'
+      vmImage: 'macos-latest'
     variables:
       platform: 'android'
     timeoutInMinutes: 60 # how long to run the job before automatically cancelling