Node.js 24 requires a new version of the action.

This is the same deal as https://github.com/dhall-lang/setup-dhall/issues/10

Github is in the process of migrating to Node.js 24. The announcement and time schedule are: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

The last migration was trivial just to change the version numbers, but I don't know whether Node.js itself has any breaking changes.