add paper on "Formalizing Soundness Proofs of Linear PCP SNARKs" to bib.lean - #911

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: zulip/github-actions-zulip/send-message@e4c8f27c732ba9bd98ac6be0583096dea82feea5. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/