Fixed #15351 -- Corrected a missing word in the template reference docs....

Fixed #15351 -- Corrected a missing word in the template reference docs. Thanks to issackelly for the report and patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@15589 bcc190cf-cafb-0310-a4f2-bffc1f526a37