device: fix failure to open message-only window

Not sure why I was getting this, but this seems to fix it

panda/src/device/winInputDeviceManager.cxx

@@ -521,7 +521,7 @@ window_proc(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam) {
   default:
     break;
   }
-  return DefWindowProcW(hwnd, msg, wparam, lparam);
+  return DefWindowProc(hwnd, msg, wparam, lparam);
 }
 
 #ifdef HAVE_THREADS