Improve Mlflow Callbacks documentation.
I recently followed https://julsimon.medium.com/using-mlflow-with-hugging-face-transformers-4f69093a6c04 , transformers documentation on mlflow callback is not formatted properly.

![image](https://user-images.githubusercontent.com/107429941/209551361-6b546fba-d1fc-4273-b84a-e15057873857.png)

It is better to read from the source code https://github.com/huggingface/transformers/blob/accad48e5b4a98302ea396b9f15c5f1c987b6f7f/src/transformers/integrations.py#L894 than the documentation site. 
![image](https://user-images.githubusercontent.com/107429941/209551549-e7b2729f-894f-4c82-841d-4ecfe7c8f70a.png)

I am sure that in the past, I might have seen such examples over other classes. I thought may be I  should report it.