Update docs to use django-admin instead of django-admin.py
|Reported by:||Tim Graham||Owned by:||nobody|
|Has patch:||no||Needs documentation:||no|
|Needs tests:||no||Patch needs improvement:||no|
Refs #21827 and the switch to setuptools in [66f546b].
I don't think there's a reason not to make the change, although we're likely to get tickets from people using the wrong version of Django.