Cleanup packages_delete_orphaned_dependencies_worker FF

What does this MR do and why?

MR !20549 (merged) added two tables: packages_dependencies and packages_dependency_links. When a package is deleted, packages_dependency_links rows are properly deleted but rows in packages_dependencies are kept and they can become orphans.

MR !113076 (merged) introduced a cron worker to iterate on the packages_dependencies table and delete those orphaned records.

We put the changes behind a feature flag and now it's globally enabled and deemed stable. This MR is to remove the feature flag.

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

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.

Related to #38266 (closed)