[license] Update year to 2021

tests/test-license.py

@@ -1,7 +1,7 @@
 #!/usr/bin/env python3
 
 # ################################################################
-# Copyright (c) 2016-2020, Facebook, Inc.
+# Copyright (c) 2016-2021, Facebook, Inc.
 # All rights reserved.
 #
 # This source code is licensed under both the BSD-style license (found in the
@@ -138,4 +138,4 @@ def main():
     return len(invalid_files)
 
 if __name__ == "__main__":
-    sys.exit(main())
+    sys.exit(main())