Simplified Intersphinx configuration example.

docs.djangoproject.com had been updated to serve the object.inv file
from the default location, so the second tuple element can be None
(the "default" value).

docs/intro/reusable-apps.txt

@@ -274,7 +274,7 @@ this. For a small app like polls, this process isn't too difficult.
             # ...
             "django": (
                 "https://docs.djangoproject.com/en/stable/",
-                "https://docs.djangoproject.com/en/stable/_objects/",
+                None,
             ),
         }