Resolve cross join issues in ee/app/workers/vulnerabilities/orphaned_remediations_cleanup_worker.rb

What does this MR do and why?

This MR removes a non-functional cross db interaction suppression that was necessary early in the sec-decomposition process. This is no longer needed, and does not modify GitLab's behaviour.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #480161 (closed)