Node 16 is deprecated

I recently noticed a warning in my CI pipeline:

> `Node.js 16 actions are deprecated. Please update the following actions to use Node.js 20: numworks/setup-emscripten@bbc4f5e15974bc13e69fdadecfd1858ecb1c4dbb. For more information see: https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/.`