test: twitterapi: fix another possible test failure case

test/web/twitter_api/util_controller_test.exs

@@ -36,7 +36,7 @@ defmodule Pleroma.Web.TwitterAPI.UtilControllerTest do
   describe "GET /api/statusnet/config.json" do
     test "it returns the managed config", %{conn: conn} do
       Pleroma.Config.put([:instance, :managed_config], false)
-      Pleroma.Config.put([:fe, :theme], "rei-ayanami-towel")
+      Pleroma.Config.put([:fe], theme: "rei-ayanami-towel")
 
       response =
         conn