caja-actions-config-tool Icon Chooser

`caja-actions-config-tool` Icon Chooser has somewhat broken interface: it doesn't allow to extend the window with icons.

`MATE 1.26.2`

<img width="886" height="596" alt="Image" src="https://github.com/user-attachments/assets/dd31f8e3-c49e-4e99-9450-0851b3944613" />