Change icons in web UI (#27385)

Co-authored-by: Renaud Chaput <renchap@gmail.com>

app/javascript/mastodon/features/ui/components/notifications_counter_icon.js

@@ -1,10 +1,14 @@
 import { connect } from 'react-redux';
 
+import { ReactComponent as NotificationsIcon } from '@material-symbols/svg-600/outlined/notifications-fill.svg';
+
 import { IconWithBadge } from 'mastodon/components/icon_with_badge';
 
+
 const mapStateToProps = state => ({
   count: state.getIn(['notifications', 'unread']),
   id: 'bell',
+  icon: NotificationsIcon,
 });
 
 export default connect(mapStateToProps)(IconWithBadge);