Fixed #14669 -- corrected an ungrammatical sentence in the...

Fixed #14669 -- corrected an ungrammatical sentence in the internationalization docs. Thanks to steveire for the report.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@14539 bcc190cf-cafb-0310-a4f2-bffc1f526a37