Update doc tags for auth to show REST and gRPC API authorization.
Update doc tags for auth to show REST and gRPC API authorization.

GoogleCloudPlatform/dotnet-docs-samples,jsimonweb/csharp-docs-samples,GoogleCloudPlatform/dotnet-docs-samples,GoogleCloudPlatform/dotnet-docs-samples,jsimonweb/csharp-docs-samples,GoogleCloudPlatform/dotnet-docs-samples,jsimonweb/csharp-docs-samples,jsimonweb/csharp-docs-samples