Gallery: Default window height is wrong

On https://snapshots.slint.dev/master/demos/gallery/ as well as when running the gallery locally, the default height of the window cuts off several widgets at the bottom: This is how it looks like now: <img width="812" height="844" alt="Image" src="https://github.com/user-attachments/assets/9d88556e-604a-4456-a874-04a46cd10c69" /> When when making the window taller you can see the missing widgets: <img width="812" height="1037" alt="Image" src="https://github.com/user-attachments/assets/9dfa4a6a-c344-46c9-859b-5a1c90bf55a6" /> This appears to be a regression from 1.16.