Heroku tutorial's future

Heroku will [stop offering a free tier](https://blog.heroku.com/next-chapter#focus-on-mission-critical) starting 2022-11-28.

>Starting October 26, 2022, we will begin deleting inactive accounts and associated storage for accounts that have been inactive for over a year.

> Starting November 28, 2022, we plan to stop offering free product plans and plan to start shutting down free dynos and data services. We will be sending out a series of email communications to affected users.

Our Heroku tutorial should be migrated to a different provider, ideally not requiring a credit card for easier testing for people without one or those who do not want to provide their credit card.