Downgrade postgres to fix integration test

The prisma postgres test app had an error on postgres 17. Downgrade to
the latest 16.4 version.

```
ERROR:  column d.daticulocale does not exist
LINE 6:        d.daticulocale as "ICU Locale",
               ^
HINT:  Perhaps you meant to reference the column "d.datlocale".

```

test/express-prisma-postgres/docker-compose.yml

@@ -2,7 +2,7 @@ version: "3.8"
 
 services:
   postgres:
-    image: postgres
+    image: postgres:16.4
     restart: always
     environment:
       - POSTGRES_USER=my_user