### Godot version

4.0.beta12

### System information

Windows 11, RTX 3080

### Issue description

When a Window Node is created with it's Transparent flag set to true and Project Settings --> Display --> Window --> Subwindows --> Embed Subwindows is false, the Window has a black background. By cycling the transparent flag from false and back to true again, during runtime, the window's background then becomes transparent. 

### Steps to reproduce

Attempt to create a Non-embedded Subwindow with a transparent background using the appropriate flags. 

### Minimal reproduction project

Note: this project is from Reddit user [gongpha](https://www.reddit.com/user/gongpha/) and his Reddit post [Learning a Godot 4.0 Window node](https://www.reddit.com/r/godot/comments/xr8yxn/learning_a_godot_40_window_node/)

https://github.com/gongpha/godot4-window-test
}
	mainwindow_icon = (HICON)SendMessage(windows[MAIN_WINDOW_ID].hWnd, WM_GETICON, ICON_BIG, 0);
	if (mainwindow_icon) {
		SendMessage(windows[window_id].hWnd, WM_SETICON, ICON_BIG, (LPARAM)mainwindow_icon);
	}
	return window_id;
}
void DisplayServerWindows::show_window(WindowID p_id) {
	ERR_FAIL_COND(!windows.has(p_id));
	WindowData &wd = windows[p_id];
	popup_open(p_id);
	if (p_id != MAIN_WINDOW_ID) {
		_update_window_style(p_id);
	}
	if (wd.maximized) {
		ShowWindow(wd.hWnd, SW_SHOWMAXIMIZED);
		SetForegroundWindow(wd.hWnd); 
		SetFocus(wd.hWnd); 
	} else if (wd.minimized) {
		ShowWindow(wd.hWnd, SW_SHOWMINIMIZED);
	} else if (wd.no_focus || wd.is_popup) {
		
		ShowWindow(wd.hWnd, SW_SHOWNA);
	} else {
		ShowWindow(wd.hWnd, SW_SHOW);
		SetForegroundWindow(wd.hWnd); 
		SetFocus(wd.hWnd); 
	}
}
void DisplayServerWindows::delete_sub_window(WindowID p_window) {