Remove redundant fixtures and test setup
Remove redundant fixtures and test setup

In response to [^1] and [^2].

[^1]: https://github.com/alphagov/notifications-admin/pull/4180/files#r819673624
[^2]: https://github.com/alphagov/notifications-admin/pull/4180/files#r819673799

alphagov/notifications-admin,alphagov/notifications-admin,alphagov/notifications-admin,alphagov/notifications-admin