Update omniauth-oauth2 and remove error verification monkey-patch

What does this MR do and why?

The fix for this was submitted upstream at https://github.com/omniauth/omniauth-oauth2/pull/144

We patched this for a security release in #27241 (closed).

How to set up and validate locally

It's a bit involved since you need to set up an OAuth2 provider, refer to https://gitlab.com/gitlab-org/security/gitlab/-/merge_requests/1731#manual-qa for some basic instructions 😀

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #27241 (closed)