docs: Fix import/export example bug

Author: fritz-c

examples/storybooks/__snapshots__/storyshots.test.js.snap

@@ -3222,15 +3222,15 @@ exports[`Storyshots Basics treeData import/export 1`] = `
         , name: 
         N3
         , parent: 
-        3
+        2
       </li>
       <li>
         id: 
         4
         , name: 
         N4
         , parent: 
-        4
+        3
       </li>
     </ul>
   </div>

examples/storybooks/tree-data-io.js

@@ -35,7 +35,7 @@ export default class App extends Component {
     }).map(({ node, path }) => ({
       id: node.id,
       name: node.name,
-      parent: path.length > 1 ? path[path.length - 1] : null,
+      parent: path.length > 1 ? path[path.length - 2] : null,
     }));
 
     return (