Unreviewed update to the watchlist.

Removing 'mkwst+watchlist@chromium.org' from committers.py and the
watchist file; moving to 'mkwst@chromium.org' instead.

* Scripts/webkitpy/common/config/committers.py:
* Scripts/webkitpy/common/config/watchlist:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@148503 268f45cc-cd09-0410-ab3c-d52691b4dbfc