UICommon: Avoid including Xrandr.h

Xlib has really terrible headers that declare non-namespaced
macros and typedefs for common words.

Just wasted 10 minutes trying to figure out why a unit test failed
to build before I remembered it was Xrandr.h conflicting with our
enum class members again.

To fix the issue, this removes the Display* parameter from the
EnableScreensaver function (which was unused) so we don't have
to include Xrandr.h anymore.

Source/Core/DolphinQt2/MainWindow.cpp

@@ -972,10 +972,7 @@ void MainWindow::NetPlayQuit()
 void MainWindow::EnableScreenSaver(bool enable)
 {
 #if defined(HAVE_XRANDR) && HAVE_XRANDR
-  UICommon::EnableScreenSaver(
-      static_cast<Display*>(QGuiApplication::platformNativeInterface()->nativeResourceForWindow(
-          "display", windowHandle())),
-      winId(), enable);
+  UICommon::EnableScreenSaver(winId(), enable);
 #else
   UICommon::EnableScreenSaver(enable);
 #endif