Delete and recreate Heroku review apps that are missing a corresponding build

After a rebase, apps often encounter this error in the provision stage of the CI workflow:

Error: No review app build found for app id.

This is caused by a mismatch of commit hashes and can only be remedied by deleting the review app and creating a new one. Currently this process must be done manually by going into the Heroku GUI.

This release allows this to be achieved automatically by the script that runs as part of the CI process, saving developers time and avoiding confusion.