[fix] A @JsonProperty cannot be used for enums

I applied the same pattern than others enum

Author: aheritier

src/main/java/org/zendesk/client/v2/model/CommentType.java

@@ -1,13 +1,21 @@
 package org.zendesk.client.v2.model;
 
-import com.fasterxml.jackson.annotation.JsonProperty;
-
 /**
  * https://developer.zendesk.com/api-reference/ticketing/tickets/ticket_comments/
  */
 public enum CommentType {
 
-    @JsonProperty("Comment") COMMENT,
-    @JsonProperty("VoiceComment") VOICE_COMMENT;
+    COMMENT("Comment"),
+    VOICE_COMMENT("VoiceComment");
+
+    private final String name;
+
+    CommentType(String name) {
+        this.name = name;
+    }
 
+    @Override
+    public String toString() {
+        return name;
+    }
 }