Revision call duration.

Author: Haiping Chen

src/Plugins/BotSharp.Plugin.Twilio/Models/ConversationalVoiceRequest.cs

@@ -39,9 +39,6 @@ public class ConversationalVoiceRequest : VoiceRequest
     [FromForm]
     public int MachineDetectionDuration { get; set; }
 
-    [FromForm]
-    public int Duration { get; set; }
-
     [FromForm]
     public int CallDuration { get; set; }