[ci] Produce installers with public download links (#5259)

Context: 68be8d8

We can produce public facing download links for our installers by adding
`/public/` to our blob storage upload path.

build-tools/automation/azure-pipelines.yaml

@@ -1232,7 +1232,7 @@ stages:
  parameters:
  BuildPackages: $(System.DefaultWorkingDirectory)/storage-artifacts
  AzureContainerName: $(Azure.Container.Name)
- AzureUploadLocation: $(Build.DefinitionName)/$(Build.BuildId)/$(Build.SourceBranchName)/$(Build.SourceVersion)
+ AzureUploadLocation: $(Build.DefinitionName)/public/$(Build.BuildId)/$(Build.SourceBranchName)/$(Build.SourceVersion)
  SourceDirectory: $(System.DefaultWorkingDirectory)/xamarin-android
 
  - script: cp $(System.DefaultWorkingDirectory)/storage-artifacts/*.pkg $(Build.ArtifactStagingDirectory)