[1.0.X] Fixed #11026, a small typo in the regroup template tag docstring....

[1.0.X] Fixed #11026, a small typo in the regroup template tag docstring. Thanks, mitsuhiko. Backport of [10687] from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.0.X@10688 bcc190cf-cafb-0310-a4f2-bffc1f526a37