Remove redundant function (needs Go >= 1.23)

[BooleanCat]

Make use of Go 1.23's news maps and slices iterators to replace a hand-crafted map key sorter.

This relies on Go 1.23 being the minimum version - once it's updaded in go.mod I'll modify this commit to remove my change to go.mod.

[BooleanCat]

I'm guessing you follow the same support policy for Go versions as the language itself? (i.e. this minor and the previous)

[AkihiroSuda]

I'm guessing you follow the same support policy for Go versions as the language itself? (i.e. this minor and the previous)

Yes, so we still have to support Go 1.22

[BooleanCat]

@AkihiroSuda understood, I'll leave this open until 1.24 or if you want to close I'll open another when it's released.