Fix Heroku review app deployments

[patch0]

Status

What's changed?

• Updates app.json to remove requirement for Postgres 14
• Adds in some other env variables to make review apps work more easily (bypass auth, sentry env, no salesforce)
• Adds in the ruby buildpack explicitly
• Seeds the database after deploy

Steps to perform after deploying to production

Doesn't affect prod 🤞🏻

[github-actions]

Test coverage

91.97% line coverage reported by SimpleCov.
Run: https://github.com/RaspberryPiFoundation/editor-api/actions/runs/28241055356

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[mwtrew]

Thanks for fixing this :)

One thing to note, we might also need to change config.host to use HEROKU_APP_NAME in this case, like ExCS have (1, 2)