fix: ajuste na config do hex

mix.exs

@@ -35,6 +35,7 @@ defmodule NotificationDispatcher.MixProject do
       {:amqp, "~> 1.6.0"},
       {:poison, "~> 3.1"},
       {:timex, "~> 3.5"},
+      {:ex_doc, "~> 0.23", only: :dev, runtime: false}
     ]
   end
 end