Mark 20230427555555 as obsolete

This migration marks the 20230427555555 BackfillHiddenOnMergeRequests Advanced search migration as obsolete.

This MR will still need changes to remove references to the migration in the code. At the moment the gitlab-housekeeper is not always capable of removing all references so you must check the diff and pipeline failures to confirm if there are any issues. It is the responsibility of the assignee (picked from groupglobal search) to push those changes to this branch.

You can read more about the process for marking Advanced search migrations as obsolete in https://docs.gitlab.com/ee/development/search/advanced_search_migration_styleguide.html#deleting-advanced-search-migrations-in-a-major-version-upgrade.

As part of our process we want to ensure all Advanced search migrations have had at least one required stop to process the migration. Therefore we can mark any Advanced search migrations added before the last required stop as obsolete.

This change was generated by gitlab-housekeeper using the Keeps::MarkOldAdvancedSearchMigrationsAsObsolete keep.

To provide feedback on your experience with gitlab-housekeeper please comment in #442003.