[Feature flag] Cleanup extract_mr_diff_deletions

Summary

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

• Previous FF issue: #372060 (closed)
• Merge request: !96455 (merged)

Owners

• Team: groupsource code
• Most appropriate slack channel to reach out to: #g_create_source-code-be
• Best individual to reach out to: @vyaklushin

What are we expecting to happen?

Projects that had problems with deletion will be processed successfully.

What might happen if this goes wrong?

Projects scheduled for a deletion are not deleted.

What can we monitor to detect problems with this?

• https://log.gprd.gitlab.net/goto/6a755f20-2dde-11ed-8656-f5f2137823ba (Production)
• https://log.gprd.gitlab.net/goto/b60139f0-2e92-11ed-b86b-d963a1a6788e (Production successful removal)
• https://nonprod-log.gitlab.net/goto/b636fcc0-2dde-11ed-af31-918941b0065a (Staging)

Cleaning up the feature flag

• Create a merge request to remove extract_mr_diff_deletions 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 extract_mr_diff_deletions --dev
  • /chatops run feature delete extract_mr_diff_deletions --staging
  • /chatops run feature delete extract_mr_diff_deletions
• Close this rollout issue.