Use 'premium-0' Redis add-ons on QA for better parity.

[DFurnes]

What's this PR do?

This pull request updates our QA instances to use the base paid premium-0 Heroku Redis add-ons on QA, since that offers us better parity when testing changes on QA.

How should this be reviewed?

👀

Any background context you want to provide?

We don't want to be surprised again by something that works on QA & doesn't on prod! 💣

Relevant tickets

References Pivotal #177948981.

Checklist

• [ ] This PR has been added to the relevant Pivotal card.