Do not look at preferred_binding on handle_logout_request

Signed-off-by: Ivan Kanakarakis <ivan.kanak@gmail.com>

Author: c00kiemon5ter

src/saml2/client.py

@@ -666,12 +666,11 @@ def handle_logout_request(
             status = status_message_factory("Wrong user",
                                             STATUS_UNKNOWN_PRINCIPAL)
 
-        preferred_binding = self.config.preferred_binding.get("single_logout_service")
         response_bindings = {
             BINDING_SOAP: [BINDING_SOAP],
             BINDING_HTTP_POST: [BINDING_HTTP_POST, BINDING_HTTP_REDIRECT],
             BINDING_HTTP_REDIRECT: [BINDING_HTTP_REDIRECT, BINDING_HTTP_POST],
-        }.get(binding, preferred_binding)
+        }.get(binding)
 
         if sign is None:
             sign = self.logout_responses_signed