Add a missing parenthese

Summary: Closes https://github.com/facebook/react-native/pull/6724

Differential Revision: D3115214

fb-gh-sync-id: 2b97ed162c15d8e6ad4ce4906a8b6fcba44864ca
fbshipit-source-id: 2b97ed162c15d8e6ad4ce4906a8b6fcba44864ca

Libraries/StyleSheet/StyleSheet.js

@@ -110,7 +110,7 @@ module.exports = {
    *   }
    * });
    *
-   * StyleSheet.flatten([styles.listItem, styles.selectedListItem]
+   * StyleSheet.flatten([styles.listItem, styles.selectedListItem])
    * // returns { flex: 1, fontSize: 16, color: 'green' }
    * ```
    * Alternative use: