Removed django.contrib.sites from ALWAYS_INSTALLED_APPS in runtests.py. It was causing a test error for people who don't have SITE_ID set, and none of the tests required it, anyway

git-svn-id: http://code.djangoproject.com/svn/django/trunk@5887 bcc190cf-cafb-0310-a4f2-bffc1f526a37