fix dead links #275
Description
These links are dead and flagged by CI: https://github.com/celestiaorg/nmt/actions/runs/11020197107/job/30604443948?pr=274
ERROR: 3 dead links found!
[✖] https://github.com/informalsystems/quint/blob/main/tutorials/README.md → Status: 404
[✖] https://github.com/informalsystems/quint/blob/main/doc/quint-cheatsheet.pdf → Status: 404
[✖] https://github.com/informalsystems/quint/blob/main/doc/builtin.md → Status: 404