### Godot version

4.1.1

### System information

linux

### Issue description

- When favoriting a path in a `FileDialog`, clicking on it travels to `path/to/dir/`.
- When going up a level from there, it doesn't go to `path/to` but to `path/to/dir` (without the `/`).

[simplescreenrecorder-2023-08-18_09.38.37.webm](https://github.com/godotengine/godot/assets/71937306/00c20ad3-292f-4961-84ed-dbc64906df52)

The problem is either (or both) that:
 - loaded path has a trailing `/`
 - parent dir of `stuff/` is considered to be `stuff`

### Steps to reproduce

favorite a directory and use the feature to navigate to it

### Minimal reproduction project

any (i.e. the project manager's "new project" dialog has one)
mode_thumbnails->set_icon(theme_cache.mode_thumbnails);
	mode_list->set_icon(theme_cache.mode_list);
	if (is_layout_rtl()) {
		dir_prev->set_icon(theme_cache.forward_folder);
		dir_next->set_icon(theme_cache.back_folder);
	} else {
		dir_prev->set_icon(theme_cache.back_folder);
		dir_next->set_icon(theme_cache.forward_folder);
	}
	dir_up->set_icon(theme_cache.parent_folder);
	refresh->set_icon(theme_cache.reload);
	favorite->set_icon(theme_cache.favorite);
	show_hidden->set_icon(theme_cache.toggle_hidden);
	fav_up->set_icon(theme_cache.favorites_up);
	fav_down->set_icon(theme_cache.favorites_down);
}
void EditorFileDialog::_favorite_selected(int p_idx) {