test: fix called_once_withh in test_create_netbox_object_check_mode_false

Calling `MagicMock.called_once_with` returns a mock object and asserting
that always succeeds. Replace this call with
`MagicMock.assert_called_with` in
`test_create_netbox_object_check_mode_false` since
`endpoint_mock.create` is called twice: once in the test setup and once
by `_create_netbox_object`.

Signed-off-by: Benjamin Drung <benjamin.drung@canonical.com>

Author: bdrung

tests/unit/module_utils/test_netbox_base_class.py

@@ -300,7 +300,7 @@ def test_create_netbox_object_check_mode_false(
     serialized_obj, diff = mock_netbox_module._create_netbox_object(
         endpoint_mock, normalized_data
     )
-    assert endpoint_mock.create.called_once_with(normalized_data)
+    endpoint_mock.create.assert_called_with(normalized_data)
     assert serialized_obj.serialize() == return_value
     assert diff == on_creation_diff