Update gitlab_omniauth-ldap to v2.2.0

What does this MR do and why?

This relaxes the dependency of OmniAuth to make it possible to upgrade to OmniAuth v2: https://gitlab.com/gitlab-org/gitlab/-/issues/30073

No code changes are present: https://my.diffend.io/gems/gitlab_omniauth-ldap/2.1.1/2.2.0

How to set up and validate locally

1. In your gdk.yml:

openldap:
  enabled: true

1. Run gdk update and gdk reconfigure.

See gitlab-development-kit!2672 (diffs) for more details.

MR acceptance checklist

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