Check whether Google OAuth URL is deprecated

[CremboC]

https://github.com/permutive/fs2-google-pubsub/blob/d70fc53535e4eeaf3da2b83e9c08d664c9ce4b52/fs2-google-pubsub-http/src/main/scala/com/permutive/pubsub/http/oauth/GoogleOAuth.scala#L34

Allegedly the above URL is deprecated and we should use https://oauth2.googleapis.com/token. I can't find anything exact and all Google documentation regarding this endpoint have disappearing from the Cloud documentation.

I found grahamearley/FirestoreGoogleAppsScript#43 which solves authentication problems (which we, as of writing this, don't have) by simply changing the URL.

[alejandrohdezma]

This is now not an issue on this library since it doesn't handle authentication. However the underlying issue has been fixed on the library to control authentication (gcp-auth).