Fixed #8373 -- Corrected a bad link in the admin.txt documentation. Thanks...

Fixed #8373 -- Corrected a bad link in the admin.txt documentation. Thanks jarrow for catching my mistake.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@8422 bcc190cf-cafb-0310-a4f2-bffc1f526a37