ci: bump actions/* to Node.js 24 runtime - #115

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: Swatinem/rust-cache@9d47c6ad4b02e050fd481d890b2ea34778fd09d6. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/