REFACTOR: Remove `Discourse.SiteSettimgs` from @setting decorator

app/assets/javascripts/discourse/app/lib/computed.js

@@ -162,6 +162,6 @@ export function endWith() {
 **/
 export function setting(name) {
   return computed(function() {
-    return Discourse.SiteSettings[name];
+    return this.siteSettings[name];
   });
 }

test/javascripts/lib/computed-test.js

@@ -25,7 +25,8 @@ discourseModule("lib:computed", {
 });
 
 QUnit.test("setting", function(assert) {
-  var t = EmberObject.extend({
+  let t = EmberObject.extend({
+    siteSettings: this.siteSettings,
     vehicle: setting("vehicle"),
     missingProp: setting("madeUpThing")
   }).create();