ci: fix failing e2e test

Author: kiaking

examples/shopping-cart/api/shop.js

@@ -15,7 +15,7 @@ export default {
   buyProducts (products, cb, errorCb) {
     setTimeout(() => {
       // simulate random checkout failure.
-      (Math.random() > 0.5 || navigator.userAgent.indexOf('PhantomJS') > -1)
+      (Math.random() > 0.5 || navigator.webdriver)
         ? cb()
         : errorCb()
     }, 100)