publications: remove out-of-date sections and link to community website instead

[Kha]

I don't see us keeping any of these lists up to date, so I think we should concentrate on our own publications. Note though that the community website does not have a list of courses and is actually missing these specific publications. Perhaps some/all of them should be added to the community site? /cc @leanprover-community

[robertylewis]

I'll add these to the community site. For future reference, the publication list is generated from https://github.com/leanprover-community/leanprover-community.github.io/blob/newsite/lean.bib, feel free to add anything that seems relevant!

[leodemoura]

merged