Bump base bound to <4.20

mentioned in issue ghc/ghc#23563 (closed)

approved this merge request

added 9 commits

• 734dfe63...e5bddb12 - 8 commits from branch master
• 001f8fc4 - Bump base bound to <4.20

Compare with previous version

merged

BTW @bgamari could you possibly grant @July541 (https://hackage.haskell.org/user/July541) maintainership over array at https://hackage.haskell.org/package/array/maintainers/edit?

Done.