[API] Generator: Update license header

Author: picandocodigo

elasticsearch-api/utils/thor/templates/method.erb

@@ -1,6 +1,19 @@
-# 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.
 
 module Elasticsearch
 <%- if @current_api == :xpack -%>