Update volume paths in production override for nginx

Simplify the volume paths by removing unnecessary `backend` prefix. This ensures consistency with other configurations and avoids potential path conflicts.

docker-compose.prod.override.yml

@@ -16,8 +16,8 @@ services:
   nginx:
     image: nginx:1.23
     volumes:
-      - ./backend/static:/usr/share/nginx/html/static:ro
-      - ./backend/media:/usr/share/nginx/html/media:ro
+      - ./static:/usr/share/nginx/html/static:ro
+      - ./media:/usr/share/nginx/html/media:ro
     networks:
       - traefik
     labels: