Update io.ex (#12800)

Fix newlines in documentation for IO module

Author: gmile

lib/elixir/lib/io.ex

@@ -593,11 +593,11 @@ defmodule IO do
 
   Another example where you might want to collect a user input
   every new line and break on an empty line, followed by removing
-  redundant new line characters (`"\n"`):
+  redundant new line characters (`"\\n"`):
 
       IO.stream(:stdio, :line)
-      |> Enum.take_while(&(&1 != "\n"))
-      |> Enum.map(&String.replace(&1, "\n", ""))
+      |> Enum.take_while(&(&1 != "\\n"))
+      |> Enum.map(&String.replace(&1, "\\n", ""))
 
   """
   @spec stream(device, :line | pos_integer) :: Enumerable.t()