Investigate redis usage in Detroit

[ludtkemorgan]

We removed all usages of redis from core, however it still exists in Detroit. It is being used by a throttling system as well as queueing services (e.g listings-notifications.ts).

One reason we removed redis was because it wasn't working as intended in heroku for core. We should investigate to make sure that the redis functionality is actually working as intended and if migrating off of it is a better option.

The outcome of this ticket should determine what to do with redis in Detroit.