Remove not needed macrocallback code

This code added in 6951f0c was made obsolete in aee7fbc (v1.1). Correct macrocallback handling was added in 04f151b (v1.10) and since then macro caller arg is passed to typespecs as `term()` instead of `Macro.Env.t()`

Author: lukaszsamson

lib/iex/lib/iex/introspection.ex

@@ -630,7 +630,6 @@ defmodule IEx.Introspection do
   defp format_callback({{kind, name, _arity}, specs}) do
     Enum.map(specs, fn spec ->
       Typespec.spec_to_quoted(name, spec)
-      |> Macro.prewalk(&drop_macro_env/1)
       |> format_typespec(kind, 0)
     end)
   end
@@ -659,11 +658,6 @@ defmodule IEx.Introspection do
     format_typespec(callbacks, :optional_callbacks, 0)
   end
 
-  defp drop_macro_env({name, meta, [{:"::", _, [_, {{:., _, [Macro.Env, :t]}, _, _}]} | args]}),
-    do: {name, meta, args}
-
-  defp drop_macro_env(other), do: other
-
   @doc """
   Prints the types for the given module and type documentation.
   """