fixed a liner issue

Author: scmacdon

python/test_tools/neptune_graph_stubber.py

@@ -1,3 +1,6 @@
+# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+# SPDX-License-Identifier: Apache-2.0
+
 import boto3
 import io
 from botocore.stub import Stubber