Update pipe-operator.md (#859)
Update pipe-operator.md (#859)

Clarified the part of Elixir that function arity doesn't matter to.
nscyclone/elixir-school,ElixirVietnam/elixir-school,huydx/elixir-school,huydx/elixir-school,doomspork/elixir-school,psantos10/elixir-school,psantos10/elixir-school,nscyclone/elixir-school,ElixirVietnam/elixir-school,doomspork/elixir_school,erickgnavar/elixir-school,nscyclone/elixir-school,yuriibodarev/elixir-school,psantos10/elixir-school,yuriibodarev/elixir-school,doomspork/elixir-school,ElixirVietnam/elixir-school,doomspork/elixir-school,erickgnavar/elixir-school,doomspork/elixir_school,doomspork/elixir_school,erickgnavar/elixir-school,yuriibodarev/elixir-school,nscyclone/elixir-school,huydx/elixir-school