Demote invite_group_to_project_spec from reliable suite

What does this MR do?

Removes 9_data_stores/project/invite_group_to_project_spec.rb from the :reliable tests to unblock deployments

E2E Test Failure issue(s)

#426033 (closed) #423385 (closed)

Check-list

• General code guidelines check-list
  • Code review guidelines
  • Style guides
• Demotion test check-list
  • (Optionally) In case of an emergency (e.g. blocked deployments), consider adding labels to pick into auto-deploy (Pick into auto-deploy priority1 severity1).
• 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.