[Feature flag] Cleanup gitlab_managed_cluster_resources

Summary

This issue is to cleanup the gitlab_managed_cluster_resources feature flag, after the feature flag has been enabled by default for an appropriate amount of time in production.

Agent managed resources is going be a permanent feature going forward.

Related: [Feature flag] Rollout of `gitlab_managed_clust... (#514901 - closed)

Owners

• Team: groupenvironments
• Most appropriate slack channel to reach out to: #g_environments
• Best individual to reach out to: @tigerwnz
• PM: NAME

Stakeholders

Expectations

What might happen if this goes wrong?

Cleaning up the feature flag

• Specify in the issue description if this feature will be removed completely or will be productized as part of the Feature Flag cleanup
• Create a merge request to remove gitlab_managed_cluster_resources 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 gitlab_managed_cluster_resources --dev --pre --staging --staging-ref --production
• Close this rollout issue.