examples/with-react-helmet: upgrade react-helmet to v6.0.0 (#12000)

examples/with-react-helmet/package.json

@@ -11,6 +11,6 @@
     "next": "latest",
     "react": "^16.7.0",
     "react-dom": "^16.7.0",
-    "react-helmet": "^5.1.3"
+    "react-helmet": "^6.0.0"
   }
 }

examples/with-react-helmet/pages/_app.js

 import React from 'react'
-import Helmet from 'react-helmet'
+import { Helmet } from 'react-helmet'
 
 function MyApp({ Component, pageProps }) {
   return (

examples/with-react-helmet/pages/_document.js

 import Document, { Head, Main, NextScript } from 'next/document'
-import Helmet from 'react-helmet'
+import { Helmet } from 'react-helmet'
 
 export default class extends Document {
   static async getInitialProps(...args) {

examples/with-react-helmet/pages/about.js

 import React from 'react'
-import Helmet from 'react-helmet'
+import { Helmet } from 'react-helmet'
 
 export default function About() {
   return (