at-supports-014 out of date

The test
contributors/opera/submitted/css3-conditional/at-supports-014.html
is out of date based on the working group resolution committed in
this changeset: https://dvcs.w3.org/hg/csswg/rev/34b185ae3bac

The attached patch should, I believe, turn it into a correct test.
If you agree that this is correct, feel free to commit it (and
preferably let me know), or ask me to commit it.

-David

-- 
𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla                           http://www.mozilla.org/   𝄂