Oauth callback `/users/auth/google_oauth2/callback` sometimes exceeds 60s worker timeout.

This request sometimes exceeds the worker timeout

Visible in the logs here: https://log.gitlab.net/goto/d984adfbed4f6b3063ce0798b3b94433

I assume this happens because don't put a deadline on the OAuth2::Client that makes a request to an external service. Which could exceed the request deadline.

We should add a timeout to the request to this external service based on the Gitlab::RequestContext#request_deadline.