.github/workflows: Remove the unused retest workflow

[timflannagan]

Signed-off-by: timflannagan timflannagan@gmail.com

Description of the change:
Remove the largely unused retest workflow that's responsible for retesting failing github actions.

Motivation for the change:
Cleanup

Reviewer Checklist

• Implementation matches the proposed design, or proposal is updated to match implementation
• Sufficient unit test coverage
• Sufficient end-to-end test coverage
• Docs updated or added to /doc
• Commit messages sensible and descriptive
• Tests marked as [FLAKE] are truly flaky
• Tests that remove the [FLAKE] tag are no longer flaky

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: timflannagan

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[awgreene]

/lgtm

[openshift-ci]

New changes are detected. LGTM label has been removed.