refactor(core): remove @Injectable as only classes that are instantiated via DI need it

modules/angular2/src/platform/worker_render.dart

@@ -59,7 +59,6 @@ class UIMessageBusSource extends IsolateMessageBusSource {
  * Wrapper class that exposes the Isolate
  * and underlying {@link MessageBus} for lower level message passing.
  */
-@Injectable()
 class WebWorkerInstance {
   Isolate worker;
   MessageBus bus;