E2E: Use Omnibus configurators in OAuth e2e job

What does this MR do and why?

Switch the OAuth e2e test job to use Omnibus configurators for Facebook and GitHub OAuth. These configurators were added in gitlab-qa in gitlab-qa!1235 (merged)

Note: This should be merged only after gitlab-qa!1242 (merged) is merged and a new gitlab-qa version has been released and the ref is updated in this project.

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