Remove now unused capture_err

Author: QuinnWilton

lib/elixir/test/elixir/protocol_test.exs

@@ -3,10 +3,6 @@ Code.require_file("test_helper.exs", __DIR__)
 defmodule ProtocolTest do
   use ExUnit.Case, async: true
 
-  defp capture_err(fun) do
-    ExUnit.CaptureIO.capture_io(:stderr, fun)
-  end
-
   doctest Protocol
 
   {_, _, sample_binary, _} =