game: Automatic update of arrow position (#5729)

Currently, zones must keep track of which cards they move in order to
manually call `updatePath` on arrows.

This patch sets the `ItemSendsScenePositionChanges` flag on
`ArrowTarget`s to automatically update arrow positions without requiring
zones to keep track of that information.

cockatrice/src/game/cards/abstract_card_item.cpp

@@ -331,5 +331,5 @@ QVariant AbstractCardItem::itemChange(QGraphicsItem::GraphicsItemChange change,
         update();
         return value;
     } else
-        return QGraphicsItem::itemChange(change, value);
+        return ArrowTarget::itemChange(change, value);
 }