Revert 190089 &quotTurn on SyncedNotifications for Dev, Canary, and ...&quot

      reverting cause it's causing server-side problems where sync becomes unavailable.
crbug.com/223556

> Turn on SyncedNotifications for Dev, Canary, and Unknown channel
> 
> Turning it on in Dev and Canary will allow us to gather feedback during the development process.
> 
> BUG=22205
> 
> 
> Review URL: https://chromiumcodereview.appspot.com/12617010

TBR=petewil@chromium.org
Review URL: https://codereview.chromium.org/13030006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@190471 0039d316-1c4b-4281-b951-d872f2087c98