[GCM] Remove the line I forgot to remove at GCMClientImpl::StartMCSLogin

BUG=284553
R=fgorski@chromium.org
TBR=zea@chromium.org

Review URL: https://codereview.chromium.org/147703006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@248277 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 248277