Add missing license header

Differential Revision: D66995586

Pull Request resolved: pytorch#988

Author: tonykao8080

torchx/schedulers/aws_sagemaker_scheduler.py

@@ -1,4 +1,10 @@
 #!/usr/bin/env python3
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
 
 import getpass
 import os