Gruntfile.js: use the same targets as JSHint for JSCS to avoid duplication.

Gruntfile.js

@@ -68,16 +68,16 @@ module.exports = function (grunt) {
         options: {
           'requireParenthesesAroundIIFE': true
         },
-        src: ['Gruntfile.js', 'grunt/*.js']
+        src: '<%= jshint.grunt.src %>'
       },
       src: {
-        src: 'js/*.js'
+        src: '<%= jshint.src.src %>'
       },
       test: {
-        src: 'js/tests/unit/*.js'
+        src: '<%= jshint.test.src %>'
       },
       assets: {
-        src: ['docs/assets/js/application.js', 'docs/assets/js/customizer.js']
+        src: '<%= jshint.assets.src %>'
       }
     },