chore: re-vendor protobuf.lua from lua-protobuf v0.6.11 - #85

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4, JohnnyMorganz/stylua-action@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

gh-actions-lua: Cache restored: lua:luajit-2.1:linux:x64: