Clean up parseMediaQueryList from BisonCSSParser

Following https://codereview.chromium.org/171383002/ BisonCSSParser::parseMediaQueryList is no longer used. This CL removes that unused code.

BUG=

Review URL: https://codereview.chromium.org/201573006

git-svn-id: svn://svn.chromium.org/blink/trunk@169808 bbb929c8-8fbe-4397-9dbb-9b2b20218538