FIX: Ember test imports, again (#16203)

We use that import also outside of tests…

app/assets/javascripts/discourse-loader.js

@@ -164,6 +164,10 @@ var define, requirejs;
       "@ember/object/internals": {
         guidFor: Ember.guidFor,
       },
+      "@ember/test": {
+        registerWaiter: Ember.Test && Ember.Test.registerWaiter,
+        unregisterWaiter: Ember.Test && Ember.Test.unregisterWaiter,
+      },
       I18n: {
         // eslint-disable-next-line
         default: I18n,

app/assets/javascripts/test-shims.js

@@ -26,16 +26,6 @@ define("htmlbars-inline-precompile", () => {
   };
 });
 
-define("@ember/test", () => {
-  // eslint-disable-next-line no-undef, discourse-ember/global-ember
-  const { registerWaiter, unregisterWaiter } = Ember.Test;
-
-  return {
-    registerWaiter,
-    unregisterWaiter,
-  };
-});
-
 let _app;
 define("@ember/test-helpers", () => {
   let helpers = {