Update dependency postgres_backup to v18-4

requirements.yml

@@ -60,7 +60,7 @@
   version: v18.6-0
   name: postgres
 - src: git+https://github.com/mother-of-all-self-hosting/ansible-role-postgres-backup.git
-  version: v18-3
+  version: v18-4
   name: postgres_backup
 - src: git+https://github.com/mother-of-all-self-hosting/ansible-role-prometheus.git
   version: v3.14.0-0