xdg-shell: Remove the serial from popup_done

It doesn't serve any purpose, as it's a serial that the client gave to
the server when starting the popup, which the client already has.

Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>

clients/window.c

@@ -4727,7 +4727,7 @@ menu_redraw_handler(struct widget *widget, void *data)
 }
 
 static void
-handle_popup_popup_done(void *data, struct xdg_popup *xdg_popup, uint32_t serial)
+handle_popup_popup_done(void *data, struct xdg_popup *xdg_popup)
 {
 	struct window *window = data;
 	struct menu *menu = window->main_surface->widget->user_data;

desktop-shell/shell.c

@@ -3315,8 +3315,7 @@ shell_surface_send_popup_done(struct shell_surface *shsurf)
 	if (shell_surface_is_wl_shell_surface(shsurf))
 		wl_shell_surface_send_popup_done(shsurf->resource);
 	else if (shell_surface_is_xdg_popup(shsurf))
-		xdg_popup_send_popup_done(shsurf->resource,
-					  shsurf->popup.serial);
+		xdg_popup_send_popup_done(shsurf->resource);
 }
 
 static void

protocol/xdg-shell.xml

@@ -415,7 +415,6 @@
 	that is, when the users clicks a surface that doesn't belong
 	to the client owning the popup surface.
       </description>
-      <arg name="serial" type="uint" summary="serial of the implicit grab on the pointer"/>
     </event>
 
   </interface>