Add deprecation warnings to docstrings

[albertvillanova]

Add deprecation warnings to docstrings.

This PR adds deprecation notices to docstrings for documentation consistency: the docstring should match the actual behavior of the code.

This approach is better than removing it entirely because:

• The parameter still exists in the code and will accept values (even if it shows a warning)
• Users need the documentation of the parameter to better understand the deprecation message

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

[albertvillanova]

[qgallouedec]

for rloo it's not properly rendered

[albertvillanova]

for rloo it's not properly rendered

Yes, I discovered this bug in doc-builder: the warning is not properly rendered when the parameter description is under a parameter subsection > Deprecated parameters.

• For the rest of classes, I just put the deprecated params under no subsection, just at the root parameters section Args:
• But for RLOOConfig:
  • There already exist other param subsections:

    Parameters:
        > Parameters that control the model and reference model
    
        model_init_kwargs (`str`, `dict[str, Any]`, *optional*):

  • Therefore the possible solutions are:
    • Either fix the rendering by putting the deprecated parameters in the root Args section, before all the rest of parameters: but I don't think it makes sense to document the deprecated parameters before the functional ones
    • Or put the deprecated parameters in a > Deprecated parameters subsection after all the other params, with their malformed rendering
      • I could open an issue (or PR) in doc-builder and eventually have these parameters properly rendered

What do you think?

[albertvillanova]

I opened an issue in doc-builder to report this bug:

• Malformed Deprecated rendering when parameter is under an Args subsection doc-builder#627

[qgallouedec]

lgtm!

[qgallouedec]

I mean, let's keep the malformed warning, not a big deal