🐛 Fixed fetching labels and offers in the editor (#20815)

ref https://linear.app/tryghost/issue/ONC-263/
- labels dropdown in sign up card was not successfully fetching labels
- offers dropdown suffered the same fate

When introducing the second editor instance, it appears we ran into some
race conditions with the Ember tasks used to fetch the resources. The
init instance was beating the other to the punch, and so the state was
never successfully updated, as it is only fetched once on mounting the
card.

ghost/admin/app/components/koenig-lexical-editor.js

@@ -248,7 +248,7 @@ export default class KoenigLexicalEditor extends Component {
         // don't rethrow, Lexical will attempt to gracefully recover
     }
 
-    @task({restartable: true})
+    @task({restartable: false})
     *fetchOffersTask() {
         if (this.offers) {
             return this.offers;
@@ -257,7 +257,7 @@ export default class KoenigLexicalEditor extends Component {
         return this.offers;
     }
 
-    @task({restartable: true})
+    @task({restartable: false})
     *fetchLabelsTask() {
         if (this.labels) {
             return this.labels;