Revert "Switch to operator= for item updates"

This reverts commit d0b22d21bb.

pcbnew/api/api_handler_pcb.cpp

@@ -478,7 +478,7 @@ HANDLER_RESULT<ItemRequestStatus> API_HANDLER_PCB::handleCreateUpdateItemsIntern
         {
             BOARD_ITEM* boardItem = *optItem;
             commit->Modify( boardItem );
-            *boardItem = *item;
+            boardItem->SwapItemData( item.get() );
             boardItem->Serialize( newItem );
         }