Find alternative to click-completion which is now in maintenance mode

As https://github.com/click-contrib/click-completion 

> is in maintenance mode only. No new features will be added.

an alternative should be found so that it can be migrated away from. At the moment it is only used in the

https://github.com/scikit-hep/pyhf/blob/35acce8917513d316c8fee83f32239af7d63257c/pyproject.toml#L69

extra, so there is a low impact on pyhf as a project overall.