### 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
Point2 pos = p_pos;
	if ((root != p_item || !hide_root) && p_item->is_visible()) {
		h = compute_item_height(p_item) + theme_cache.v_separation;
		if (pos.y < h) {
			if (drop_mode_flags == DROP_MODE_ON_ITEM) {
				section = 0;
			} else if (drop_mode_flags == DROP_MODE_INBETWEEN) {
				section = pos.y < h / 2 ? -1 : 1;
			} else if (pos.y < h / 4) {
				section = -1;
			} else if (pos.y >= (h * 3 / 4)) {
				section = 1;
			} else {
				section = 0;
			}
			for (int i = 0; i < columns.size(); i++) {
				int w = get_column_width(i);