OpenAI max_token is deprecated

[cescoffier]

max_tokens (Deprecated):  The maximum number of [tokens](https://platform.openai.com/tokenizer) that can be generated in the chat completion. This value can be used to control [costs](https://openai.com/api/pricing/) for text generated via API.

This value is now deprecated in favor of max_completion_tokens, and is not compatible with [o1 series models](https://platform.openai.com/docs/guides/reasoning).

We would need to switch to the new parameter only if the provider is OpenAI.