Remove QA tests from quarantine and remove FF

What does this MR do?

The tests were failing because of a change that was behind a couple of feature flags. The feature flags have been removed and the feature is now fully active, and the tests are passing.

This also removes the gitaly_distributed_reads feature flag which was removed from the codebase a few releases ago.

E2E Test Failure issue(s)

• #332234 (closed)
• #322814 (closed)
• #331989 (closed)

Check-list

• General code guidelines check-list
  • Code review guidelines
  • Style guides
• Dequarantine test check-list
  • Follow the Dequarantining Tests guide.
  • Confirm the test consistently passes on the target GitLab environment(s).
    • [-] (Optionally) Trigger a manual GitLab-QA pipeline against a specific GitLab environment using the RELEASE variable from the package-and-qa job of the current merge request.