Docs for finetuning inconsistent with behavior

[chschrae]

In the finetuning job description https://platform.openai.com/docs/api-reference/fine-tuning/object

there is a required hyperparameter with n_epochs, but in the example and at runtime the other hyperparameters are also returned.

This document should match that.

There is also a case to be made that there should be one object for both the request and the return but that must have been an intentional design choice.

I created a pr from a forked repo:
#308