Reasoning models like `o1` and `o3` and their `-mini` variants
report errors if we try to configure `max_response_tokens` (which
ultimately influences the `max_tokens` field in the API request):

> invalid_request_error: Unsupported parameter: 'max_tokens' is not supported with this model. Use 'max_completion_tokens' instead. (param: max_tokens) (code: unsupported_parameter)

`max_completion_tokens` is not yet supported by baibot, so the best we
can do is at least get rid of `max_response_tokens` (`max_tokens`).

Ref: db9422740c