DEV: use lib path for scroll-top util function

Author: tyb-talks

assets/javascripts/discourse/routes/custom-wizard-step.js

@@ -1,7 +1,7 @@
 import { action } from "@ember/object";
 import Route from "@ember/routing/route";
 import { service } from "@ember/service";
-import { scrollTop } from "discourse/mixins/scroll-top";
+import { scrollTop } from "discourse/lib/scroll-top";
 import I18n from "I18n";
 import { getCachedWizard } from "../models/custom-wizard";