Update docker-compose.yml

Author: Jesús Gorroñogoitia Cruz

samples/stamp/atos/Citygo/nginx/docker-compose.yml

@@ -17,7 +17,7 @@ services:
       - port=5432
       - POSTGRES_DB=citygo_malaga
       - POSTGRES_USER=citygo
-      - POSTGRES_PASSWORD=5X6sdoq0!?az=v2aSX
+      - POSTGRES_PASSWORD=$POSTGRES_PASSWORD
       - PGDATA=/var/lib/postgresql/data/pgdata
     volumes:
       - postgres_data:/var/lib/postgresql/data/