Update license headers in xplat

Summary: Per title.

Reviewed By: danielbuechele

Differential Revision: D15166958

fbshipit-source-id: 26f0a6d7523be3192833fd3995bc9f5e948816a6

xplat/Flipper/FlipperStateUpdateListener.h

@@ -1,11 +1,9 @@
-/*
- *  Copyright (c) 2018-present, Facebook, Inc.
- *
- *  This source code is licensed under the MIT license found in the LICENSE
- *  file in the root directory of this source tree.
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
  *
+ * This source code is licensed under the MIT license found in the LICENSE
+ * file in the root directory of this source tree.
  */
-
 #pragma once
 
 class FlipperStateUpdateListener {