fix logging out from editor page

closes #6514
- removes transition.abort from the signout method because it can override the ember-simple-auth's page refresh

ghost/admin/app/routes/signout.js

@@ -18,7 +18,6 @@ export default AuthenticatedRoute.extend(styleBody, {
         this.get('notifications').clearAll();
         if (canInvoke(transition, 'send')) {
             transition.send('invalidateSession');
-            transition.abort();
         } else {
             this.send('invalidateSession');
         }