[Bug-1042713] Remove notification icons

- Removed notification icons from the status bar
- Added new ambient notification
Also (haha sorry, so many 'Also's), why not use the `utilitytrayshow` event? In any case, this code should be added to the `handleEvent` function below. And I would prefer we factor `this.toaster.className = '';` into a function that describes what you are doing. Something like `function hideNotificationIndicator()` or something.