wayland: Don't assert non-recursing in gdk_window_destroy

While we do not have subwindows in Wayland, we do create an
artificial root window. When the display is closed, the root
window gets destroyed, causing recursing to be true for the
toplevel windows.

gdk/wayland/gdkwindow-wayland.c

@@ -1617,8 +1617,6 @@ gdk_wayland_window_destroy (GdkWindow *window,
 
   g_return_if_fail (GDK_IS_WINDOW (window));
 
-  /* We don't have nested windows */
-  g_return_if_fail (!recursing);
   /* Wayland windows can't be externally destroyed; we may possibly
    * eventually want to use this path at display close-down
    */