Change icons in web UI (#27385)

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

app/javascript/styles/application.scss

@@ -12,7 +12,6 @@
 @import 'mastodon/forms';
 @import 'mastodon/accounts';
 @import 'mastodon/statuses';
-@import 'mastodon/boost';
 @import 'mastodon/components';
 @import 'mastodon/polls';
 @import 'mastodon/modal';