Temporarily make the OAuth job manual

What does this MR do and why?

gitlab-qa!1242 (merged) introduces a breaking change where the the Test::Integration::OAuth scenario has been removed.

The oauth job that uses the scenario will be updated to use Test::instance::Image in !136158 (diffs)

Until the change from gitlab-qa has been properly propagated, we need to disable auto-running the oauth job to avoid failures.

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