fix: correct gettext usage for application publish error message

--bug=1058890 --user=王孝刚 【应用】应用未发布状态下对话，提示语国际化不对 https://www.tapd.cn/62980211/s/1744119

Author: wxg0103

apps/chat/serializers/chat.py

@@ -419,8 +419,7 @@ def open(self):
                 '-create_time')[0:1].first()
             if application_version is None:
                 raise AppApiException(500,
-                                      gettext(
-                                          "The application has not been published. Please use it after publishing."))
+                                      _("The application has not been published. Please use it after publishing."))
         if application.type == ApplicationTypeChoices.SIMPLE:
             return self.open_simple(application)
         else: