Swap from React Helmet to Unhead (#38896)

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

@@ -2,9 +2,10 @@ import { useCallback, useRef } from 'react';
 
 import { defineMessages, useIntl, FormattedMessage } from 'react-intl';
 
-import { Helmet } from 'react-helmet';
 import { NavLink, Switch, Route } from 'react-router-dom';
 
+import { Helmet } from '@unhead/react/helmet';
+
 import TrendingUpIcon from '@/material-icons/400-24px/trending_up.svg?react';
 import { Column } from 'mastodon/components/column';
 import type { ColumnRef } from 'mastodon/components/column';