### 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
}
		wd.was_maximized = wd.maximized;
		if (wd.pre_fs_valid) {
			GetWindowRect(wd.hWnd, &wd.pre_fs_rect);
		}
		int cs = window_get_current_screen(p_window);
		Point2 pos = screen_get_position(cs) + _get_screens_origin();
		Size2 size = screen_get_size(cs);
		wd.fullscreen = true;
		wd.maximized = false;
		wd.minimized = false;
		_update_window_style(p_window, false);
		MoveWindow(wd.hWnd, pos.x, pos.y, size.width, size.height, TRUE);
		
		
		SystemParametersInfoA(SPI_GETMOUSETRAILS, 0, &restore_mouse_trails, 0);
		if (restore_mouse_trails > 1) {
			SystemParametersInfoA(SPI_SETMOUSETRAILS, 0, 0, 0);
		}
	}
	
	if (mouse_mode == MOUSE_MODE_CONFINED || mouse_mode == MOUSE_MODE_CONFINED_HIDDEN) {
		RECT crect;
		GetClientRect(wd.hWnd, &crect);
		ClientToScreen(wd.hWnd, (POINT *)&crect.left);
		ClientToScreen(wd.hWnd, (POINT *)&crect.right);
		ClipCursor(&crect);
	}
}
DisplayServer::WindowMode DisplayServerWindows::window_get_mode(WindowID p_window) const {