Change the format of the error responses
To stick with the HF API. See https://github.com/huggingface/datasets-server/issues/466#issuecomment-1195528239

- [x] rename the `message` field to `error`
- [x] remove the `status_code` field
- [x] let the `cause_xxx` fields
- [x] Once it's deployed, we will have to run make refresh-cache-errors from an admin pod
Change the format of the error responses: To stick with the HF API. See https://github.com/huggingface/datasets-server/issues/466#issuecomment-1195528239

- [x] rename the `message` field to `error`
- [x] remove the `status_code` field
- [x] let the `cause_xxx` fields
- [x] Once it's deployed, we will have to run make refresh-cache-errors from an admin pod