Remove unnecessary constructor.

Author: tgancheva

src/OneBitSoftware.Utilities.OperationResult/Errors/OperationError.cs

@@ -4,12 +4,7 @@
 
 public class OperationError
 {
-    public OperationError(string message)
-    {
-        this.Message = message;
-    }
-
-    public OperationError(string message, int code)
+    public OperationError(string message, int? code = null)
     {
         this.Message = message;
         this.Code = code;