Remove `group_owners_to_disable_two_factor` FF

What does this MR do and why?

The group_owners_to_disable_two_factor feature flag has been enabled in GitLab.com and deemed safe. We proceed here to remove the flag.

Screenshots or screen recordings

N/A

How to set up and validate locally

N/A

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Cleaning up the feature flag

• Create a merge request to remove group_owners_to_disable_two_factor feature flag. Ask for review and merge it.
  • Remove all references to the feature flag from the codebase.
  • Remove the YAML definitions for the feature from the repository.
  • Create a changelog entry.
• Ensure that the cleanup MR has been deployed to both production and canary. If the merge request was deployed before the code cutoff, the feature can be officially announced in a release blog post.
  • /chatops run auto_deploy status <merge-commit-of-cleanup-mr>
• Close the feature issue to indicate the feature will be released in the current milestone.
• If not already done, clean up the feature flag from all environments by running these chatops command in #production channel:
  • /chatops run feature delete group_owners_to_disable_two_factor --dev
  • /chatops run feature delete group_owners_to_disable_two_factor --staging
  • /chatops run feature delete group_owners_to_disable_two_factor
• Close this rollout issue.