cmd/praefect: Improve style of test for removal of replicaton jobs
The test we have which verifies that removal of replication jobs works
as expected for the praefect remove-repository
subcommand is quite
hard to read. Furthermore, many of the conditions aren't as strict as
they could theoretically be.
Refactor the test to match modern coding style and tighten it to assert conditions that should be true. This hopefully helps to nail down why our CI is hanging from time to time in this job.
Note: I couldn't reproduce the linked issue, but in order to not keep it around any longer I'm marking this with a fixes tag. In case the same issue still applies we should just create a new issue.
Fixes #3944 (closed)