Removed unneeded attribute

src/Discord.Net.Core/API/Rest/CreateGuildBanParams.cs

@@ -1,9 +1,6 @@
 #pragma warning disable CS1591
-using Newtonsoft.Json;
-
 namespace Discord.API.Rest
 {
-    [JsonObject(MemberSerialization = MemberSerialization.OptIn)]
     public class CreateGuildBanParams
     {
         public Optional<int> DeleteMessageDays { get; set; }