Adjust for Git Beyond 2026 - #484

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. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

Summary report available at: https://github.com/C2SM/c2sm.github.io/actions/runs/38215069030#summary-114697798006