Resolve cross DB issues in ee/app/workers/vulnerabilities/mark_dropped_as_resolved_worker.rb

What does this MR do and why?

This MR removes a suppression of a cross database interaction that was flagged early in the sec-decomposition but is no longer applicable under the current configurations and settings. It's also possible the underlying cross interaction was remediated in a different MR. Regardless, the green CI suite indicates that no cross interaction failures are being actively raised, so this is safe to remove.

(It also does nothing in production.)

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 #482726 (closed)