Fixed #10897 -- Modified use of ngettext to ungettext in admin change...

Fixed #10897 -- Modified use of ngettext to ungettext in admin change messages. Thanks to zuber for the report and patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@10677 bcc190cf-cafb-0310-a4f2-bffc1f526a37