Bump golang.org/x/net to v0.61.0 to fix HTTP/2 CVEs - #222

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v2, actions/upload-artifact@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/