[3.2.x] Fixed typo in docs/ref/contrib/admin/index.txt.
[3.2.x] Fixed typo in docs/ref/contrib/admin/index.txt.

Backport of dacc307d9396516e7d3609b7b91e2ec545c84ebc from main

wkschwartz/django,koordinates/django,koordinates/django,wkschwartz/django,wkschwartz/django,koordinates/django,wkschwartz/django,koordinates/django