Fix t:Range.t/2 (#10833)
Fix t:Range.t/2 (#10833)

We need to be explicit and define the step field, otherwise IEx and ExDoc will spec it as "term()"

    (1)> t Range.t/2
    @type t(first, last) :: %Range{first: first, last: last, step: term()
ggcampinho/elixir,elixir-lang/elixir,ggcampinho/elixir,pedrosnk/elixir,kelvinst/elixir,michalmuskala/elixir,pedrosnk/elixir,kelvinst/elixir,kimshrier/elixir,kimshrier/elixir,joshprice/elixir