Gerrit doesn't allow arbitrary non-member emails for now,
thus removign this feature until either Gerrit allows it,
or we have a per-repo opt-in way.

TBR=andybons@chromium.org
BUG=604377

Review URL: https://codereview.chromium.org/1895863002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@299988 0039d316-1c4b-4281-b951-d872f2087c98