Enable users to trust remote code in samsum dataset

[mreso]

What does this PR do?

Currently the samsum dataset fails with a ValueError as we need to allow remote code execution in
https://github.com/meta-llama/llama-recipes/blob/9b3dabcaac78980eae40005bbc8b1a8276c82af3/src/llama_recipes/datasets/samsum_dataset.py#L11

This PR adds an option to the dataset config to activate that flag without modifying any code.

Fixes # (issue)

Feature/Issue validation/testing

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• Test B
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• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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Thanks for contributing 🎉!

[wukaixingxp]

LGTM!