Do not use Data.Semigroup.Option type on base >=4.16.0.0 (i.e. GHC >=9.2.1)

[msakai]

As @Mikolaj reported on https://github.com/mstksg/backprop/pull/19#issuecomment-1010063543 , the current master branch fails to compile on GHC 9.2 not only due to the simplified subsumption (#19) but also due to the removal of Data.Semigroup.Option on base >=4.16.0.0.

See also:

• https://hackage.haskell.org/package/base-4.15.0.0/docs/Data-Semigroup.html#t:Option

  Deprecated: will be removed in GHC 9.2; use Maybe instead.

• https://hackage.haskell.org/package/base-4.16.0.0/docs/Data-Semigroup.html

This PR fixes the latter problem.

I confirmed that GHC 9.2 can compile this PR + #19 with Vinyl 322476778d11223ac40f1e1c3faddc007eaef72a (I did not use the master branch of Vinyl because of https://github.com/VinylRecords/Vinyl/issues/157) + https://github.com/VinylRecords/Vinyl/issues/156 fix.

[Mikolaj]

Vinyl presumably has this [edit: compatibility with GHC 9.2.1] fixed in the just released version.

[Bodigrim]

@mstksg any chance to merge this please? (As a Hackage trustee I revised existing releases with base < 4.16 to prohibit unbuildable configurations)

[mstksg]

thanks! :) apologies for the delay!