Remove the old WebKit watchlist

It has not been edited since April and shows no signs of being in use,
WATCHLISTS in the root is where the action is. Remove to save others
the trouble of figuring that out.

BUG=none

Review URL: https://codereview.chromium.org/31223002

git-svn-id: svn://svn.chromium.org/blink/trunk@160035 bbb929c8-8fbe-4397-9dbb-9b2b20218538