Avoid retrying controller tests due to data not being reset

What does this MR do and why?

Do not retry controller tests because rspec-retry cannot properly reset the controller which may contain data from last attempt.

See !73360 (merged)

• Don't squash this merge request because each commits are fixing different tests

Hidden broken tests

• https://gitlab.com/gitlab-org/gitlab/-/jobs/1740470213
  • This is concerning that it's expecting a worker is not performing, yet it's performing. Upon retrying then it's not performing and it's passing.
  • This is because the maintainer can push to the fork due to having allow_maintainer_to_push as true by default

How to set up and validate locally

0. Revert !73360 (merged) locally so we have a broken controller test to try.
1. Run env RETRIES=1 rspec 'spec/controllers/projects/merge_requests_controller_spec.rb[1:8:2:3:1:1:1]' and see it fails. (expected, because it's broken)
2. Run env RETRIES=2 rspec 'spec/controllers/projects/merge_requests_controller_spec.rb[1:8:2:3:1:1:1]' and see it passes. (not expected, because retrying something broken should not pass)
3. Apply this merge request.
4. Run env RETRIES=2 rspec 'spec/controllers/projects/merge_requests_controller_spec.rb[1:8:2:3:1:1:1]' and see it fails. (expected, because now we never retry controller tests)

MR acceptance checklist

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