[idd] apply resolution after the final replug

Preserve the requested display mode across intermediate swap chains when
rapid resolution changes cause replugs to be coalesced. Apply and clear
the mode only once the final replacement swap chain is ready.

idd/LGIdd/CIndirectDeviceContext.h

@@ -187,7 +187,6 @@ public:
   void ReplugMonitor();
 
   void OnMonitorDestroyed(IDDCX_MONITOR monitor);
-  void OnAssignSwapChain();
   void OnSwapChainAssigned();
   void OnSwapChainReleased();
   void OnSwapChainReady();