App doesn't start: undefined symbol: gdk_x11_drawable_get_xid

To keep it short, the app crashes printing this when trying to run it:
```sh
$ flatpak run io.github.Rangi42.tilemap-studio
/usr/lib/x86_64-linux-gnu/libgtk-3.so.0: undefined symbol: gdk_x11_drawable_get_xid
```

I'm using this version: https://github.com/flathub/io.github.Rangi42.tilemap-studio/commit/eb488074f708479a7fcd80fba49044a0702902e0 (or Flathub remote commit `a81d6033aee93c1b2261905b985e3c3fc66e3d7fe5e8af818567b62bc90b8314`).

This seems to be an issue with the 25.08 runtime as reverting to a 24.08 one works:
```sh
sudo flatpak update --commit=852febc9702582726840c69cb395940ddccc399df1eb46f46af3ab114fcabb9a io.github.Rangi42.tilemap-studio
```

Reproduce the failure with `flatpak run io.github.Rangi42.tilemap-studio`, then compare the referenced 25.08 Flathub commit with the working 24.08 commit. Inspect the application manifest and runtime-related changes in those commits; done means the app launches successfully on the 25.08 runtime without the undefined-symbol error.

Written by the indexing model from the issue text.