Adds to #1010 add high prio to heartbeat

[timgl]

Changes

• Attempts to fix "Configuration error" warning routinely appears #1010 by adding a higher prio to the worker
• See this thread: Clarify support for task priority with redis backend celery/celery#4028 redis priority support is poorly documented and there seems to be some confusion around how it actually works.

Checklist

• All querysets/queries filter by Team (if applicable)
• Backend tests (if applicable)
• Cypress E2E tests (if applicable)

[mariusandra]

Let's see if it works!

[mariusandra]

I merged it, yet there was one cypress test that was failing. I hope it was just a flaky test and that this didn't break anything real...