Update license headers

Author: stevejgordon

src/Nest/XPack/DataStreams/Migrate/MigrateToDataStreamResponse.cs

@@ -1,7 +1,22 @@
-// Licensed to Elasticsearch B.V under one or more agreements.
-// Elasticsearch B.V licenses this file to you under the Apache 2.0 License.
-// See the LICENSE file in the project root for more information
-
+/*
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+ 
  namespace Nest
 {
 	public class MigrateToDataStreamResponse : AcknowledgedResponseBase { }