Delete unnecessary condition on expected_error_code
As reported by @AndreaFrancis (see: https://github.com/huggingface/datasets-server/pull/1418#discussion_r1340621923), the condition on `expected_error_code` can be removed because it equals `None`.
Delete unnecessary condition on expected_error_code: As reported by @AndreaFrancis (see: https://github.com/huggingface/datasets-server/pull/1418#discussion_r1340621923), the condition on `expected_error_code` can be removed because it equals `None`.