Fix whitespace in headers (#7980)

The script that strips providesModule is very sensitive.

Test plan:

Searched for providesModule in build. No more.

reactComponentExpect used to have problems too but doesn't seem
to anymore. Don't know why.

src/addons/shallowCompare.js

@@ -6,8 +6,8 @@
  * LICENSE file in the root directory of this source tree. An additional grant
  * of patent rights can be found in the PATENTS file in the same directory.
  *
-* @providesModule shallowCompare
-*/
+ * @providesModule shallowCompare
+ */
 
 'use strict';
 

src/renderers/dom/client/renderSubtreeIntoContainer.js

@@ -6,8 +6,8 @@
  * LICENSE file in the root directory of this source tree. An additional grant
  * of patent rights can be found in the PATENTS file in the same directory.
  *
-* @providesModule renderSubtreeIntoContainer
-*/
+ * @providesModule renderSubtreeIntoContainer
+ */
 
 'use strict';
 

src/renderers/shared/stack/reconciler/ReactInstanceType.js

@@ -1,4 +1,4 @@
- /**
+/**
  * Copyright 2016-present, Facebook, Inc.
  * All rights reserved.
  *
@@ -6,8 +6,8 @@
  * LICENSE file in the root directory of this source tree. An additional grant
  * of patent rights can be found in the PATENTS file in the same directory.
  *
- * @flow
  * @providesModule ReactInstanceType
+ * @flow
  */
 
 'use strict';