Fixed license header.

Signed-off-by: Vahid <vnoroozi@nvidia.com>

nemo/collections/asr/modules/multi_head_attention.py

@@ -14,6 +14,21 @@
 # limitations under the License.
 #
 
+# Copyright 2017 Johns Hopkins University (Shinji Watanabe)
+#
+# Licensed 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.
+#
+
 """
 Part of this code is adopted from https://github.com/espnet/espnet
 """