Spanish docs - Fix nits and wording
# What does this PR do?
Fix wording and nits in the merged Spanish documentation.


## Before submitting
- [x] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
@sgugger links to current docs that don't exist (eg `./main_classes/pipelines`) don't work. Do you think it would be worth linking them to the English docs while the Spanish versions become available? Or should we wait?

fyi @osanseviero <|||||>_The documentation is not available anymore as the PR was closed or merged._<|||||>I had been told that links to page that don't exist in one language would be automatically resolved to the English version, cc @mishig25 <|||||>Currently, the links lead to an error if the doc is not yet translated. For example, this fragment in [`autoclass_tutorial`](https://huggingface.co/docs/transformers/main/es/autoclass_tutorial) leads a to an error for not having [model_doc/auto.mdx](https://github.com/huggingface/transformers/blob/main/docs/source/en/model_doc/auto.mdx)
 translated yet.
> Finalmente, las clases AutoModelFor te permiten cargar un modelo preentrenado para una tarea dada (revisa [aquí](https://huggingface.co/docs/transformers/main/es/model_doc/auto) para conocer la lista completa de tareas disponibles).

Please let me know if any help is required. Meanwhile, I will summon more community for the translation.<|||||>This PR fixes some wording and format in the Spanish docs. It would be ready to merge IMO.

I opened issue #17461 regarding the problem with the links.<|||||>Thanks for fixing!