Address 3994 pytest warnings

[joeyorlando]

What would you like to see!

As of the writing of this issue we have > 3900 warnings when running our backend tests (see here for an example CI build):

================ 1 failed, 2872 passed, 3994 warnings in 45.36s ================

Deliverables
Address (the majority of) the pytest warnings.

Product Area

Other

Anything else to add?

No response

[github-actions]

The current version of Grafana OnCall, at the time this issue was opened, is v1.6.2. If your issue pertains to an older version of Grafana OnCall, please be sure to list it in the PR description. Thank you 😄!