Exclude HF token from serialization

[sysradium]

Currently only api_key is being proactively excluded from dumps on any object.
However, HF related objects, like TransformersLLM, define token as a SecretStr: https://github.com/argilla-io/distilabel/blob/main/src/distilabel/models/llms/huggingface/transformers.py#L110

That leads either to a failure to save:

generation_model_1.save()
*** TypeError: Type is not JSON serializable: SecretStr

Or a successful save:

generation_model_1.save(format="yaml")

That would produce a YAML file with:

token: !!python/object:pydantic.types.SecretStr
  _secret_value: hf_lkjreglkn290Elnwef111j

That is unusable. And leads to a failure like:

distiset = pipeline.run()             
distiset.save_to_disk(distiset_path="dataset") 

ConstructorError: could not determine a constructor for the tag 'tag:yaml.org,2002:python/object:pydantic.types.SecretStr'
  in "<unicode string>", line 105, column 16:
            token: !!python/object:pydantic.types.S ...

A comment says like it should have been filtered automatically out since it is a SecretStr, however, nowhere can I use an encoder defined to do this.

So I went with the smallest change, just including the token into the exclusion list.