fixup tests for list_nodes_by_episode_sorted

fix credo

test/radiator/outline_test.exs

@@ -771,8 +771,7 @@ defmodule Radiator.OutlineTest do
 
       num_nodes_without_parents =
       tree
-      |> Enum.filter(fn n -> n.parent_id == nil end)
-      |> Enum.count
+      |> Enum.count(fn n -> n.parent_id == nil end)
 
       assert num_nodes_without_parents == 3
     end