fix(动态): 修复动态话题下请求动态列表报错问题

@mutoe

Author: medz

app/API2/Controllers/Feed/TopicFeed.php

@@ -56,7 +56,7 @@ public function __invoke(ListFeedsForATopicRequest $request, FeedTopicLinkModel
                     ->withTrashed()
                     ->with('certification');
             },
-            'pinnedComments' => function ($query) {
+            'feed.pinnedComments' => function ($query) {
                 return $query->with([
                     'user',
                     'user.certification',