Update PostgreSQL volume path in setup documentation for 18+

Author: vlauciani

docs/src/setup/index.md

@@ -136,7 +136,7 @@ services:
       POSTGRES_PASSWORD: 'npmpass'
       POSTGRES_DB: 'npm'
     volumes:
-      - ./postgres:/var/lib/postgresql/data
+      - ./postgresql:/var/lib/postgresql
 ```
 
 ::: warning