[1.0.X] Small edit to the caching docs.

Turns out, super-lightning is not faster than normal lightning. :-)

Backport of r9949 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.0.X@9950 bcc190cf-cafb-0310-a4f2-bffc1f526a37