Fix typo in app / hello.js template (#42335)

Removes the extra `}` in the url

<!--
Thanks for opening a PR! Your contribution is much appreciated.
To make sure your PR is handled as smoothly as possible we request that
you follow the checklist sections below.
Choose the right checklist for the change that you're making:
-->

packages/create-next-app/templates/app/js/pages/api/hello.js

@@ -1,4 +1,4 @@
-// Next.js API route support: https://nextjs.org/docs/api-routes/introduction}
+// Next.js API route support: https://nextjs.org/docs/api-routes/introduction
 
 export default function handler(req, res) {
   res.status(200).json({ name: 'John Doe' })