fix(docs): update fake data command

docs/developer/setup/docker.md

@@ -264,8 +264,7 @@ You can create local data to mimic a live environment.
 Add some fake data to populate the database. The following command creates 25 artists with random albums, tracks, and metadata.
 
 ```sh
-command="from funkwhale_api.music import fake_data; fake_data.create_data()"
-echo $command | docker compose run --rm -T api funkwhale-manage shell -i python
+docker compose exec -T api funkwhale-manage shell -i python <<< "from funkwhale_api.music import fake_data; fake_data.create_data(super_user_name='YOURNAMEHERE')"
 ```
 
 This will launch a development funkwhale instance with a super user having `COMPOSE_PROJECT_NAME` as username and `funkwhale` as password. Libraries, listenings and music data will be associated with the superuser :