Update docs `Enum.reduce/2` (#6442)
Update docs `Enum.reduce/2` (#6442)

The documentation for `Enum.reduce/2` references `Enumerable.reduce/3` for use of a different accumulator. However, the `Enum` module has a `reduce/3` function that does exactly this, so it makes more sense to reference that one instead of the more complicated `Enumerable.reduce/3` function.
pedrosnk/elixir,beedub/elixir,joshprice/elixir,michalmuskala/elixir,kimshrier/elixir,kimshrier/elixir,elixir-lang/elixir,antipax/elixir,gfvcastro/elixir,beedub/elixir,gfvcastro/elixir,ggcampinho/elixir,lexmag/elixir,lexmag/elixir,antipax/elixir,kelvinst/elixir,kelvinst/elixir,pedrosnk/elixir,ggcampinho/elixir