Remove keys type

[exorcist365]

Description

Include a description for your changes, including the motivation behind them.

Checklist

• [x] I've read CONTRIBUTING.md

• [x] I've considered how to best test these changes (property, unit, manually, ...) and concluded: that the documentation now displays properly

  - [ ] I updated the CHANGES.md file

[TheMC47]

You're right about the haddock docs looking bad with this type hidden... Not the brightest idea I had.

However, I don't think this type should be exposed here. If we want to expose it, either do it in XMonad.Prelude and replace the occurrences, or, better yet, maybe from core.

[slotThe]

There might also be an argument for just removing this alias. We're only using it in two places, really, so it might just unnecessarily confuse people

[exorcist365]

I mean... fair.

[TheMC47]

LGTM, just change the commit message to something more descriptive

[slotThe]

Thanks