Swap from React Helmet to Unhead (#38896)

app/javascript/mastodon/features/compose/index.tsx

@@ -2,11 +2,12 @@ import { useEffect, useCallback } from 'react';
 
 import { useIntl, defineMessages } from 'react-intl';
 
-import { Helmet } from 'react-helmet';
 import { Link } from 'react-router-dom';
 
 import type { Map as ImmutableMap, List as ImmutableList } from 'immutable';
 
+import { Helmet } from '@unhead/react/helmet';
+
 import elephantUIPlane from '@/images/elephant_ui_plane.svg';
 import EditIcon from '@/material-icons/400-24px/edit_square.svg?react';
 import PeopleIcon from '@/material-icons/400-24px/group.svg?react';