Hackage doesn't show docs for 2.4.1.3

[rybern]

Compare:

• 2.4.1.2 with working docs: https://hackage.haskell.org/package/units-2.4.1.2
• 2.4.1.3 with broken docs: https://hackage.haskell.org/package/units-2.4.1.3