E2E Test: quarantine create MR test for update-ee-to-ce job

What does this MR do?

This quarantines qa/specs/features/browser_ui/3_create/merge_request/create_merge_request_spec.rb for the update-ee-to-ce job only while the failure issue is under investigation. The failure is caused by the Create MR page having a never-ending spinner for the codeowners field AFTER we downgrade to CE. Strangely CE shouldn't have this field.

To ensure this quarantine worked as intended I had to create a pipeline with a dummy change otherwise the tests are skipped due to the MR only having quarantine changes: https://gitlab.com/gitlab-org/gitlab/-/pipelines/1031261228

• Not quarantined for GDK smoke tests: https://gitlab.com/gitlab-org/gitlab/-/jobs/5256404832#L879 ✅
• Not quarantined for package and test ee: https://gitlab-qa-allure-reports.s3.amazonaws.com/e2e-package-and-test/jmc-412361/1031283678/index.html#suites/164a0058b889d7f1a2096e0be388055b/5725315ebef7e064/ ✅
• Quarantined for https://gitlab.com/gitlab-org/gitlab/-/jobs/5257144687#L836 ✅
• Not quarantined for other CE jobs: https://gitlab-qa-allure-reports.s3.amazonaws.com/e2e-package-and-test-ce/jmc-412361/1031365580/index.html#suites/164a0058b889d7f1a2096e0be388055b/2bf1f9fd6a3d0720/

I then removed the dummy change.

E2E Test Failure issue(s)

#412361 (closed)

Check-list

• General code guidelines check-list
  • Code review guidelines
  • Style guides
• Quarantine test check-list
  • Follow the Quarantining Tests guide.
  • Confirm the test has a quarantine: tag with the specified quarantine type.
  • Note if the test should be quarantined for a specific environment.
  • (Optionally) In case of an emergency (e.g. blocked deployments), consider adding labels to pick into auto-deploy (Pick into auto-deploy priority1 severity1).
• Dequarantine test check-list
  • Follow the Dequarantining Tests guide.
  • Confirm the test consistently passes on the target GitLab environment(s).
• To ensure a faster turnaround, ask in the #quality_maintainers Slack channel for someone to review and merge the merge request, rather than assigning it directly.