Remove TODO comment about calling webView from non-ui thread.

I tried it and it turned out to be a bit slower instead of faster.

framework/src/org/apache/cordova/NativeToJsMessageQueue.java

@@ -303,8 +303,6 @@ public class NativeToJsMessageQueue {
             webView.setNetworkAvailable(true);
         }
         public void onNativeToJsMessageAvailable() {
-            // TODO(agrieve): consider running this *not* on the main thread, since it just
-            // sends a message under-the-hood anyways.
             cordova.getActivity().runOnUiThread(runnable);
         }
     }