Retire Release Post bugs check

What does this MR do and why?

The Release Post bug & performance issue check can now be done on an ongoing basis with GLQL. It doesn't need to be generated by triage ops and to ping EMs.

The new Wiki is https://gitlab.com/gitlab-org/plan-stage/plan-engineering/-/wikis/Completed-Bug-and-Performance-Issues-for-the-Release-Post.

This change proposes to remove the automation entirely.

Expected impact & dry-runs

These are strongly recommended to assist reviewers and reduce the time to merge your change.

See https://gitlab.com/gitlab-org/quality/triage-ops/-/tree/master/doc/scheduled#testing-policies-with-a-dry-run on how to perform dry-runs for new policies.

See https://gitlab.com/gitlab-org/quality/triage-ops/-/blob/master/doc/reactive/best_practices.md#use-the-sandbox-to-test-new-processors on how to make sure a new processor can be tested.

Action items

• If adding environment variables for reactive processors, update config/triage-web.yaml and .gitlab/ci/triage-web.yml
• (If applicable) Add documentation to the handbook pages for Triage Operations =>
• (If applicable) Identify the affected groups and how to communicate to them:
  • /cc @person_or_group =>
  • Relevant Slack channels =>
  • Engineering week-in-review