remove legacy io_request handlers

we don't support OTP < R15B

apps/elixir_ls_utils/lib/output_device.ex

@@ -31,24 +31,12 @@ defmodule ElixirLS.Utils.OutputDevice do
     {:noreply, s}
   end
 
-  @impl GenServer
-  def handle_info({:io_request, from, reply_as, {:put_chars, characters}}, s) do
-    output(from, reply_as, characters, s)
-    {:noreply, s}
-  end
-
   @impl GenServer
   def handle_info({:io_request, from, reply_as, {:put_chars, _encoding, module, func, args}}, s) do
     output(from, reply_as, apply(module, func, args), s)
     {:noreply, s}
   end
 
-  @impl GenServer
-  def handle_info({:io_request, from, reply_as, {:put_chars, module, func, args}}, s) do
-    output(from, reply_as, apply(module, func, args), s)
-    {:noreply, s}
-  end
-
   @impl GenServer
   def handle_info({:io_request, from, reply_as, {:requests, reqs}}, s) do
     for req <- reqs do