### 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)
popup_centered_clamped(Size2(1050, 700) * EDSCALE, 0.8);
	_focus_file_text();
}
void EditorFileDialog::_focus_file_text() {
	int lp = file->get_text().rfind(".");
	if (lp != -1) {
		file->select(0, lp);
		file->grab_focus();
	}
}
VBoxContainer *EditorFileDialog::get_vbox() {
	return vbox;
}
void EditorFileDialog::_update_theme_item_cache() {