[3.x] CheckBox icon does not update when editor's theme changes

### Tested versions

3.6.beta4 & 3.x[a885e8322db5f85bb56f1e4b3400161e2c21afd0]

### System information

Arch Linux

### Issue description

Editor's CheckBox & CheckButton icons does not update when theme changes.


_The icon is still green. It should be blue after changing the editor's theme._

### Steps to reproduce

Change your editor theme to one that icon color is different.

Find a CheckBox or CheckButton in the editor and check its icon color.

### Minimal reproduction project (MRP)

N/A

Reproduce the issue in the Godot editor by changing the editor theme, then inspect the CheckBox and CheckButton icon behavior. The work is done when both controls update their icon colors to match the selected theme after a theme change.

Written by the indexing model from the issue text.