Fix queue purge security scans migration
What does this MR do and why?
This MR fixes a bug related to a recently introduced database migration. The migration was introduced in this milestone but I have added a changelog entry anyway for the sake of transparency.
This MR does not change any queries.
Related to Purge old `security_scans` records on self-host... (!144456 - merged).
Edited by Mehmet Emin INAC