### 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
EnumRefreshRateData *data = (EnumRefreshRateData *)dwData;
	if (data->count == data->screen) {
		MONITORINFOEXW minfo;
		memset(&minfo, 0, sizeof(minfo));
		minfo.cbSize = sizeof(minfo);
		GetMonitorInfoW(hMonitor, &minfo);
		DEVMODEW dm;
		memset(&dm, 0, sizeof(dm));
		dm.dmSize = sizeof(dm);
		EnumDisplaySettingsW(minfo.szDevice, ENUM_CURRENT_SETTINGS, &dm);
		data->rate = dm.dmDisplayFrequency;
	}
	data->count++;
	return TRUE;
}
Rect2i DisplayServerWindows::screen_get_usable_rect(int p_screen) const {