[tests] `slow_unit_tests` failing intermittently

Relevant code snippet: https://gitlab.com/gitlab-org/gl-openshift/gitlab-operator/-/blob/5e2c46069e7e2cdeee9f2ab63f6070bff6466ad7/controllers/gitlab_controller_test.go#L58-60

The issue here appears to be that deleting the CR is relatively instantaneous, but the related resources take some time to be fully deleted.

This causes problems when the next Context begins, and resources from the previous release are still around. An example: you can see that the release name is crd-testing even though the tests have moved on to the context where the release name should be jobs-succeeded.