Bump postgres to 16 in dev bot

This is needed for a postgres 15 only feature now used on site

Author: ChrisLovering

docker-compose.yaml

@@ -8,7 +8,7 @@ x-restart-policy: &restart_policy
 services:
   postgres:
     << : *restart_policy
-    image: postgres:13-alpine
+    image: postgres:16-alpine
     environment:
       POSTGRES_DB: pysite
       POSTGRES_PASSWORD: pysite