### Godot version

4.0 beta 10

### System information

Windows 11 Vulkan

### Issue description

Looked through the issues list, but couldn't find something like this, sorry in advance if this has already been reported.

There is a few cases (in the pictures below) where list of Actions in Input Map may not always show a scrollbar even if the actions list overflows (I imagine this could also happen for the widget that Input Map uses).

![image](https://user-images.githubusercontent.com/39958198/210003566-cf60dbaf-921f-485b-b0a9-51ffc28d0244.png)

![New Bitmap image](https://user-images.githubusercontent.com/39958198/210004079-8eb2e6a1-0cf5-4a7c-8905-a4e3cfd0ec5d.png)

![image](https://user-images.githubusercontent.com/39958198/210004165-a6b6790b-248a-4f68-b4d0-b44b25afdf4f.png)

![image](https://user-images.githubusercontent.com/39958198/210004537-aca52194-a464-48b9-b818-24782706de45.png)


### Steps to reproduce

The pictures are clearer than anything I could write here: "a picture is worth 1000 words"

### Minimal reproduction project

N/A
prev = p_item;
	next = p_item->next;
	p_item->next = this;
	if (next) {
		parent->children_cache.clear();
	} else {
		
		
		if (!parent->children_cache.is_empty()) {
			parent->children_cache.append(this);
		}
	}
	if (tree && old_tree == tree) {
		tree->queue_redraw();
	}
	validate_cache();
}
void TreeItem::remove_child(TreeItem *p_item) {
	ERR_FAIL_NULL(p_item);
	ERR_FAIL_COND(p_item->parent != this);
	p_item->_unlink_from_tree();
	p_item->prev = nullptr;
	p_item->next = nullptr;
	p_item->parent = nullptr;
	if (tree) {
		tree->queue_redraw();
	}
	validate_cache();
}
void TreeItem::set_selectable(int p_column, bool p_selectable) {