UX: Only set user bookmarks loading state when loading (#17728)

Follow-up to 6bb77d3055

app/assets/javascripts/discourse/app/controllers/user-activity-bookmarks.js

@@ -15,7 +15,7 @@ export default Controller.extend({
 
   application: controller(),
   user: controller(),
-  loading: true,
+  loading: false,
   loadingMore: false,
   permissionDenied: false,
   inSearchMode: notEmpty("q"),

app/assets/javascripts/discourse/app/routes/user-activity-bookmarks.js

@@ -25,6 +25,8 @@ export default DiscourseRoute.extend({
       bookmarkListScrollPosition: null,
     });
 
+    controller.set("loading", true);
+
     return this._loadBookmarks(params)
       .then((response) => {
         if (!response.user_bookmark_list) {