Revert "Add code field to ReaderEvent"

This reverts commit cc3649d8.

MoyaAdmin/MoyaAdminUI/MoyaAdminLib/ReaderEvent.cs

@@ -14,6 +14,5 @@ namespace MoyaAdminLib
         public Eventuser eventuser;
         public int? printedCardId = 0;
         public string printedCardState = "";
-        public string code;
     }
 }