Mounting to /var/lib/postgres/data is no longer allowed after Postgres 18 (#1651)

I got an error when running bracket through the provided compose because
mounting directly to the postgres data directory is not allowed after
version 18

docker-compose.yml

@@ -36,4 +36,4 @@ services:
       - bracket_lan
     restart: always
     volumes:
-      - bracket_pg_data:/var/lib/postgresql/data
+      - bracket_pg_data:/var/lib/postgresql