Tweak for devcontainer docker compose (#6601)

- Do not use named volume
- Hardcode db path

.devcontainer/docker-compose.yml

@@ -7,7 +7,7 @@ services:
     expose:
       - 5432/tcp
     volumes:
-      - postgresql:/var/lib/postgresql/data:z
+      - ../dev:/var/lib/postgresql/data:z
     environment:
       POSTGRES_DB: inventree
       POSTGRES_USER: inventree_user
@@ -36,6 +36,3 @@ services:
 
     depends_on:
       - db
-
-volumes:
-  postgresql: