Fix default port mapping and indentation

Signed-off-by: Anca Iordache <anca.iordache@docker.com>

nginx-flask-mongo/docker-compose.yaml

@@ -8,15 +8,15 @@ services:
       - FLASK_SERVER_ADDR=backend:9091  
     command: /bin/bash -c "envsubst < /tmp/nginx.conf > /etc/nginx/conf.d/default.conf && nginx -g 'daemon off;'" 
     ports:
-    - 8080:80
+      - 80:80
     depends_on:
-    - backend
+      - backend
   backend:
     build: flask
     environment: 
-    - FLASK_SERVER_PORT=9091
+      - FLASK_SERVER_PORT=9091
     volumes:
-    - ./flask:/src
+      - ./flask:/src
     depends_on:
       -  mongo  
   mongo: