Update smollm3.md -- missing citation for intra-document masking

[pminervini]

The citation for intra-document masking is missing, fixed it

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[pcuenca]

Thanks a lot Pasquale! In blog posts we try to maximize readability rather than being exhaustive with citations. Personally I'm not opposed to adding this like we cited NoPE, but I'll defer to the team @eliebak @loubnabnl for their opinion. Also, we may want to use the HF papers link instead :)

[pminervini]

thanks @pcuenca, good call! just switched from arxiv to https://huggingface.co/papers 🙂