Merge pull request #3689 from joshcrews/spelling_fix

spelling `miliseconds` -> `milliseconds`

Author: josevalim

lib/ex_unit/lib/ex_unit.ex

@@ -121,7 +121,7 @@ defmodule ExUnit do
         4. or set it to infinity per run by calling "mix test --trace"
            (useful when using IEx.pry)
 
-      Timeouts are given as integers in miliseconds.
+      Timeouts are given as integers in milliseconds.
       """
     end
   end