Quarantine invite group to project spec and update quarantine templates

What does this MR do?

Quarantine invite group to project spec to unblock deployments - see #436950 (comment 1711226947)

Also small updates to Quarantine templates - updated links and formatting.

E2E Test Failure issue(s)

Failure in browser_ui/9_data_stores/project/inv... (#436950)

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.