### Godot version

4.2 dev1

### System information

Windows 10.0.19045 - Vulkan (Forward+) - dedicated NVIDIA GeForce GTX 1060 (NVIDIA; 30.0.15.1403) - Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHz (8 Threads)

### Issue description

Calling `Tree.propagate_check()` after an item is unchecked does not properly uncheck the parents. They are left in partially checked state.

It's easy to observe in theme editor:

https://github.com/godotengine/godot/assets/2223172/71d0479c-0a5e-48d3-957f-d90379a95c22



### Steps to reproduce

1. Edit a Theme resource
2. Go to Manage Items... menu
3. Go to Import Items tab
4. Unfold something
5. Check and uncheck a child checkbox

### Minimal reproduction project

N/A
int count = 0;
	for (int i = 0; i < columns.size(); i++) {
		if (p_from->is_selected(i)) {
			count++;
		}
	}
	if (p_from->get_first_child()) {
		count += _count_selected_items(p_from->get_first_child());
	}
	if (p_from->get_next()) {
		count += _count_selected_items(p_from->get_next());
	}
	return count;
}
bool Tree::_is_branch_selected(TreeItem *p_from) const {