### 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
SetPriorityClass(GetCurrentProcess(), ABOVE_NORMAL_PRIORITY_CLASS);
		DWORD index = 0;
		HANDLE handle = AvSetMmThreadCharacteristics("Games", &index);
		if (handle) {
			AvSetMmThreadPriority(handle, AVRT_PRIORITY_CRITICAL);
		}
		
		
		SetThreadPriority(GetCurrentThread(), THREAD_PRIORITY_TIME_CRITICAL);
	}
	cursor_shape = CURSOR_ARROW;
	_update_real_mouse_position(MAIN_WINDOW_ID);
	r_error = OK;
	static_cast<OS_Windows *>(OS::get_singleton())->set_main_window(windows[MAIN_WINDOW_ID].hWnd);
	Input::get_singleton()->set_event_dispatch_function(_dispatch_input_events);
}
Vector<String> DisplayServerWindows::get_rendering_drivers_func() {
	Vector<String> drivers;
#ifdef VULKAN_ENABLED
	drivers.push_back("vulkan");
#endif
#ifdef GLES3_ENABLED
	drivers.push_back("opengl3");
#endif
	return drivers;
}
DisplayServer *DisplayServerWindows::create_func(const String &p_rendering_driver, WindowMode p_mode, VSyncMode p_vsync_mode, uint32_t p_flags, const Vector2i *p_position, const Vector2i &p_resolution, int p_screen, Error &r_error) {