Fix GitHub Actions Workflow warning: Node.js 20 actions are deprecated

[fdcastel]

I can take care of this as soon #480 lands.

Node.js 20 actions are deprecated. The following actions are running on Node.js 20 and may not work as expected: (...) For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/