[Bug]: Compose modal enableDialogElement feature flag is showing extra space modal UI

When we enable enableDialogElement feature flag extra height is coming as below. This is visible in [stories](https://react.carbondesignsystem.com/?path=/story/components-composedmodal-feature-flags--enable-dialog-element)


<img width="1750" height="1982" alt="Image" src="https://github.com/user-attachments/assets/95777ecb-2c01-4913-8a3a-c2aded4cf929" />