Fix unused key issue in zh-HK (#2870)

* locale: remove unused keys in zh-HK

* locale: update json translations

* handled the untranslated strings.
* removed unused keys.

config/locales/zh-HK.yml

@@ -130,9 +130,6 @@ zh-HK:
       account_count: 已知帳號
       domain_name: 域名
       title: 已知服務站
-    moderation:
-      silenced: 被靜音
-      suspended: 被停權
     pubsubhubbub:
       callback_url: 回傳 URL
       confirmed: 確定