Notification topbar toggle should use the `aria-expanded` attribute from the start

```
On Notification button (currently named “toggle navigation”), aria-expanded=”false” is missing.
When we activate the button, then “aria-expanded=”true” appears and if we press again, true switches to false (this part is ok). aria-expanded=”false” should be present in the code before pressing the element the first time.
```

See template at https://github.com/xwiki/xwiki-platform/blob/da56c0defbd5d810035ce9164dd38ad08984a709/xwiki-platform-core/xwiki-platform-alerts/xwiki-platform-alerts-ui/src/main/resources/XWiki/Alerts/Code/AlertsMenuUIX.xml#L140-L146