webhooks: Remove unused imports.

Signed-off-by: Anders Kaseorg <andersk@mit.edu>

zerver/webhooks/insping/view.py

@@ -1,14 +1,12 @@
-from django.utils.translation import ugettext as _
-from zerver.lib.response import json_success, json_error
+from zerver.lib.response import json_success
 from zerver.lib.webhooks.common import check_send_webhook_message
 from zerver.decorator import REQ, has_request_variables, \
     api_key_only_webhook_view
-from zerver.lib.validator import check_dict, check_string
 
-from zerver.models import Client, UserProfile
+from zerver.models import UserProfile
 
 from django.http import HttpRequest, HttpResponse
-from typing import Dict, Any, Iterable, Optional
+from typing import Dict, Any
 
 import time