Fix storybook for kibana management (elastic#205299)

## Summary

Storybook broke due to recent file reorganized, this fixes it.

`yarn storybook management` will start storybook with kibana management
team content.

<img width="790" alt="Screenshot 2024-12-30 at 5 34 48 PM"
src="https://github.com/user-attachments/assets/d94637b5-cd0d-4dbc-8d25-6ed4c15d82d5"
/>

packages/kbn-management/storybook/config/main.ts

@@ -11,7 +11,9 @@ import { defaultConfig } from '@kbn/storybook';
 
 module.exports = {
   ...defaultConfig,
-  stories: ['../../**/*.stories.+(tsx|mdx)'],
+  stories: [
+    '../../../../src/platform/packages/(private|shared)/kbn-management/**/*.stories.+(tsx|mdx)',
+  ],
   reactOptions: {
     strictMode: true,
   },