Remove humps dependency

[plutopulp]

The humps package provides the same module as the pyhumps package. We want the latter but the dependencies specify both for some reason.

This PR removes humps, which removes possible ambiguities when importing humps.

[alexpearce]

Just a heads-up that poetry lock will try to update all packages within the constraints specified in the pyproject.toml, which is why there are unrelated changes in the lockfile. You can use poetry lock --no-update to avoid this (although it's typically no big deal).

[alexpearce]

Thanks!