[FIX] sale_product_configurator: remove es6 JS code

Task#1964518

This commit removes es6 code that was unintentionaly introduced
by the product configurator for better compatibility

closes odoo/odoo#32452

Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>

addons/sale_product_configurator/static/src/js/product_configurator_controller.js

@@ -292,7 +292,7 @@ var ProductConfiguratorFormController = FormController.extend({
      *
      * @param {Array} attributeValueIds
      */
-    _getAttributeValueIds(attributeValueIds) {
+    _getAttributeValueIds: function (attributeValueIds) {
         if (!attributeValueIds || attributeValueIds.length === 0){
             return false;
         }