display: Replace set_grab_op_cursor with update_cursor

Now that we don't have to regrab to change the cursor, since it's
simply the cursor on the root window, all we have to do is update
the cursor on the screen.

src/core/window.c

@@ -7057,11 +7057,7 @@ meta_window_update_keyboard_resize (MetaWindow *window,
                      &x, &y);
 
   if (update_cursor)
-    {
-      meta_display_set_grab_op_cursor (window->display,
-                                       window->display->grab_op,
-                                       window->display->grab_timestamp);
-    }
+    meta_display_update_cursor (window->display);
 }
 
 void