MAGETWO-69657: Credit Card Information disappear after user enters promotion code

- Fix code documentation

Author: Michael Yu

app/code/Magento/Checkout/view/frontend/web/js/model/payment-service.js

@@ -14,15 +14,15 @@ define([
     /**
     * Free method filter
     * @param {Object} paymentMethod
-    * @returns boolean
+    * @returns {Boolean}
     */
     var isFreePaymentMethod = function (paymentMethod) {
             return paymentMethod.method === 'free';
         },
 
         /**
          * Grabs the grand total from quote
-         * @returns number
+         * @returns {Number}
          */
         getGrandTotal = function () {
             return quote.totals().grand_total; // jscs:ignore requireCamelCaseOrUpperCaseIdentifiers