Fixed #13698 -- Removed trailing whitespace from...

Fixed #13698 -- Removed trailing whitespace from regressiontests/utils/timesince. Officially, I'm doing this because trailing whitespace is bad, but apparently it also causes test failures for some people (for reasons we can't narrow down), so there's a double win.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@13323 bcc190cf-cafb-0310-a4f2-bffc1f526a37