FIX: Lots of plugin tests were using old, non-Ember compat CLI APIs (#13320)

plugins/poll/test/javascripts/acceptance/poll-pie-chart-test.js.es6

@@ -3,6 +3,8 @@ import {
   query,
   queryAll,
 } from "discourse/tests/helpers/qunit-helpers";
+import { test } from "qunit";
+import { visit } from "@ember/test-helpers";
 
 acceptance("Rendering polls with pie charts", function (needs) {
   needs.user();