Dont post damage event from window_copy_surface

We always call this between window_draw() and attaching the window surface
so the surface we're copying to isn't visible.

clients/window.c

@@ -873,10 +873,6 @@ window_copy_surface(struct window *window,
 
 	cairo_paint (cr);
 	cairo_destroy (cr);
-
-	wl_surface_damage(window->surface,
-			  rectangle->x, rectangle->y,
-			  rectangle->width, rectangle->height);
 }
 
 static gboolean