Restore CMD with sh for prod

This should be enough for now

Dockerfile

@@ -23,4 +23,4 @@ CMD ["poetry", "run", "python", "manage.py", "runserver", "0.0.0.0:8000"]
 FROM base AS prod
 
 COPY . .
-CMD ["poetry", "run", "gunicorn", "-b", "0.0.0.0:8000", "steering.wsgi"]
+CMD ["sh", "-c", "poetry run gunicorn --bind 0.0.0.0:8000 --workers $(nproc) steering.wsgi"]