Fix intermediary responsive layout, accessibility on navigation in web UI (#19324)

* Fix intermediary responsive layout, accessibility on navigation in web UI

* `yarn test:jest -u`

Co-authored-by: Yamagishi Kazutoshi <ykzts@desire.sh>

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

@@ -11,8 +11,7 @@ import { connect } from 'react-redux';
 const Account = connect(state => ({
   account: state.getIn(['accounts', me]),
 }))(({ account }) => (
-  <Permalink href={account.get('url')} to={`/@${account.get('acct')}`}>
-    <span style={{ display: 'none' }}>{account.get('acct')}</span>
+  <Permalink href={account.get('url')} to={`/@${account.get('acct')}`} title={account.get('acct')}>
     <Avatar account={account} size={35} />
   </Permalink>
 ));