Fix test for VoiceCreateWebhook validation

Author: morsesfeeler@live.ru

tests/test_voice_webhook.py

@@ -123,9 +123,6 @@ def test_voice_create_webhook_request_validation(self):
         token = "FooBarToken"
         blank_string = '    '
 
-        with self.assertRaises(ValidationError):
-            VoiceCreateWebhookRequest(url=url)
-
         with self.assertRaises(ValidationError):
             VoiceCreateWebhookRequest(title=title)
 
@@ -139,10 +136,6 @@ def test_voice_create_webhook_request_validation(self):
         with self.assertRaises(ValidationError):
             request.url = blank_string
 
-        request.title = title + title
-        with self.assertRaises(ValidationError):
-            request.title = blank_string
-
     def test_voice_update_webhook(self):
         http_client = Mock()
         http_client.request.return_value = '''{