chore: Tree search demo type error (#38390)

* Update search.md

* Update search.md

components/tree/demo/search.md

@@ -81,7 +81,7 @@ const App: React.FC = () => {
   const [searchValue, setSearchValue] = useState('');
   const [autoExpandParent, setAutoExpandParent] = useState(true);
 
-  const onExpand = (newExpandedKeys: string[]) => {
+  const onExpand = (newExpandedKeys: React.Key[]) => {
     setExpandedKeys(newExpandedKeys);
     setAutoExpandParent(false);
   };