Added FB copyright header

packages/react-devtools-shared/src/devtools/views/Profiler/ClearProfilingDataButton.js

@@ -1,4 +1,11 @@
-// @flow
+/**
+ * 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.
+ *
+ * @flow
+ */
 
 import React, {useCallback, useContext} from 'react';
 import {ProfilerContext} from './ProfilerContext';