[1.2.X] Fixed #14578 -- Corrected a typo in the Models topic docs. Thanks to...

[1.2.X] Fixed #14578 -- Corrected a typo in the Models topic docs. Thanks to tobych for the report and patch.

Backport of [14369] from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@14370 bcc190cf-cafb-0310-a4f2-bffc1f526a37