Changing to file level use strict statement

lib/helpers/deprecatedMethod.js

@@ -1,3 +1,5 @@
+'use strict';
+
 /**
  * Supply a warning to the developer that a method they are using
  * has been deprecated.
@@ -7,9 +9,6 @@
  * @param {string} [docs] The documentation URL to get further details
  */
 module.exports = function deprecatedMethod(method, instead, docs) {
-  /*eslint-env node*/
-  'use strict';
-
   try {
     console.warn(
       'DEPRECATED method `' + method + '`.' +