chore(deps): update postgres docker tag to v15.15

Author: renovate[bot]

docker-compose.yml

@@ -147,7 +147,7 @@ services:
       - vr-net
 
   db:
-    image: postgres:15.0
+    image: postgres:15.15
     container_name: vr_postgres
     restart: always
     environment:
@@ -304,7 +304,7 @@ services:
 
   # Create the verenigingsregister database from the golden master template
   create-verenigingsregister-db:
-    image: postgres:15.0
+    image: postgres:15.15
     container_name: vr_create_verenigingsregister_db
     environment:
       - PGPASSWORD=root