Draft: Quarantine flaky BackfillUserDetails spec

What does this MR do?

This MR is to quarantine the flaky BackfillUserDetails spec that is leading to master-brokenflaky-test .

This spec has been failing intermittently in multiple pipelines - and repeatedly in the master pipeline.

Quarantining it until investigated further/or the test is stabilized.

E2E Test Failure issue(s)

#477109 (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.