(Incident 19034) Fix merge requests that were closed even if they were already merged

During gitlab-com/gl-infra/production#19034 (closed), we got internal reports of some MRs being closed after they were merged:

• gitlab-vscode-extension!2244 (closed)
• gitlab-org/quality/triage-ops!3208 (merged)

We do not know if there are more of these in the DB