bulk uses _routing while valid this produces deprecation warnings as per elastic/elasticsearch#27414

Author: Mpdreamz

src/Nest/Document/Multiple/Bulk/BulkOperation/IBulkOperation.cs

@@ -20,17 +20,17 @@ public interface IBulkOperation
 		[JsonProperty("_id")]
 		Id Id { get; set; }
 
-		[JsonProperty("_version")]
+		[JsonProperty("version")]
 		long? Version { get; set; }
 
-		[JsonProperty("_version_type")]
+		[JsonProperty("version_type")]
 		[JsonConverter(typeof(StringEnumConverter))]
 		VersionType? VersionType { get; set; }
 
-		[JsonProperty("_routing")]
+		[JsonProperty("routing")]
 		string Routing { get; set; }
 
-		[JsonProperty("_parent")]
+		[JsonProperty("parent")]
 		Id Parent { get; set; }
 
 		[JsonProperty("_timestamp")]
@@ -41,7 +41,7 @@ public interface IBulkOperation
 		[Obsolete("This feature is no longer supported on indices created in Elasticsearch 5.0.0 and up")]
 		Time Ttl { get; set; }
 
-		[JsonProperty("_retry_on_conflict")]
+		[JsonProperty("retry_on_conflict")]
 		int? RetriesOnConflict { get; set; }
 
 		object GetBody();