Move 'use strict' to file level

Change-Id: I1f0dae4aa168e77c112bcd3688c98b84e4ce5f36
diff --git a/dev/js/src/buttongroup/menu.js b/dev/js/src/buttongroup/menu.js
index 3ee7ec3..da34584 100644
--- a/dev/js/src/buttongroup/menu.js
+++ b/dev/js/src/buttongroup/menu.js
@@ -1,8 +1,8 @@
-  /**
-   * Menu to choose from in a button group.
-   */
+/**
+ * Menu to choose from in a button group.
+ */
+"use strict";
 define(['menu'], function (menuClass) {
-  "use strict";
 
   return {