Remove unnecessary env var from docs conf

Author: mfosterw

docs/conf.py

@@ -23,7 +23,6 @@
     sys.path.insert(0, os.path.abspath("/app"))  # noqa: PTH100
 django_settings = "config.settings.local"
 os.environ["DATABASE_URL"] = "sqlite:///readthedocs.db"
-os.environ["CELERY_BROKER_URL"] = os.getenv("REDIS_URL", "redis://redis:6379")
 os.environ.setdefault("DJANGO_SETTINGS_MODULE", "config.settings.local")
 django.setup()