refactor: [breaking] remove obsolete VoiceName from TalkAction

Vonage.Test/Data/NccoTests/TestTalk-request.json

@@ -5,7 +5,6 @@
     "bargeIn": true,
     "loop": "2",
     "level": "0",
-    "voiceName": "kimberly",
     "language": "en-US",
     "style": 0
   }

Vonage.Test/NccoTests.cs

@@ -220,7 +220,6 @@ public void TestTalk()
             BargeIn = true,
             Loop = "2",
             Level = "0",
-            VoiceName = "kimberly",
             Language = "en-US",
             Style = 0,
         };

Vonage/Voice/Nccos/TalkAction.cs

@@ -1,5 +1,4 @@
-using System;
-using Newtonsoft.Json;
+using Newtonsoft.Json;
 
 namespace Vonage.Voice.Nccos;
 
@@ -57,15 +56,4 @@ public class TalkAction : NccoAction
     /// </summary>
     [JsonProperty("text", Order = 1)]
     public string Text { get; set; }
-
-    /// <summary>
-    /// The name of the voice used to deliver text. You use the voiceName that has the correct language, 
-    /// gender and accent for the message you are sending. 
-    /// For example, the default voice kimberly is a female who speaks English with an 
-    /// American accent (en-US). Possible values are listed in the Text-To-Speech guide.
-    /// </summary>
-    [JsonProperty("voiceName", Order = 5)]
-    [Obsolete(
-        "This parameter has been made obsolete by the language and style fields. Please see https://developer.nexmo.com/voice/voice-api/guides/text-to-speech#locale for more details")]
-    public string VoiceName { get; set; }
 }