BMenu: don't invalidate layout when changing marked item

* The layout does not need to change. The label may change in
SetLabelFromMarked mode, but this only affects the layout of the parent
menu.
* This would crash when programatically changing the menu marked item
while the menu is open.

src/kits/interface/Menu.cpp

@@ -2592,7 +2592,6 @@ BMenu::_ItemMarked(BMenuItem* item)
 			if (ItemAt(i) != item)
 				ItemAt(i)->SetMarked(false);
 		}
-		InvalidateLayout();
 	}
 
 	if (IsLabelFromMarked() && Superitem())