Fix Route.build/14 spec for hosts and helper (#6879)

Author: lukaszsamson

lib/phoenix/router/route.ex

@@ -65,10 +65,10 @@ defmodule Phoenix.Router.Route do
           :match | :forward,
           atom,
           String.t(),
-          String.t() | nil,
+          [String.t()],
           atom,
           atom,
-          atom | nil,
+          String.t() | nil,
           list(atom),
           map,
           map,