Disable 'Ok Google' hotwording on desktop Chrome.
This feature has been removed completely from Windows, Mac and Linux
builds of Chrome. ChromeOS is unaffected.
This removes the checkbox from chrome://settings and the prompt to
activate it from the google.com
TEST=On ChromeOS (official builds), go to chrome://settings. Should see "Enable Ok Google" checkbox.
TEST=On Windows Chrome (official builds), go to chrome://settings. Should NOT see "Enable Ok Google" checkbox.