Different fix (#7815)

app/assets/javascripts/admin/controllers/admin-site-text-edit.js.es6

@@ -1,9 +1,15 @@
 import { popupAjaxError } from "discourse/lib/ajax-error";
 import { bufferedProperty } from "discourse/mixins/buffered-content";
+import computed from "ember-addons/ember-computed-decorators";
 
 export default Ember.Controller.extend(bufferedProperty("siteText"), {
   saved: false,
 
+  @computed("buffered.value")
+  saveDisabled(value) {
+    return this.siteText.value === value;
+  },
+
   actions: {
     saveChanges() {
       const buffered = this.buffered;