require_server_admin: Cut a redundant bit of request-mutation.

The only place this attribute is used is in `update_user_activity`,
called only in `process_client`, which won't happen if we end up
returning a redirect just below.  If we don't, we go and call
`add_logging_data` just after, which takes care of this already.

zerver/decorator.py

@@ -417,7 +417,6 @@ def require_server_admin(view_func):
     @wraps(view_func)
     def _wrapped_view_func(request, *args, **kwargs):
         # type: (HttpRequest, *Any, **Any) -> HttpResponse
-        request._query = view_func.__name__
         if not request.user.is_staff:
             return HttpResponseRedirect(settings.HOME_NOT_LOGGED_IN)