update docs to add the `phi-2` example
Author: susnato
Pull request: yes

# What does this PR do?

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This updates the docs as discussed [here](https://github.com/huggingface/transformers/pull/28211#issuecomment-1880115245)


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Comments:
Can you make it into a tip / warning for the mean time. 

Hi @ArthurZucker, I have added the tip/warning. 

Let me know if anything more needs to be added.

just need to rebase on main 😉 

Sorry my bad :sweat_smile: 

Done!

Thanks!