Update node version

[zangbe]

Following the recent blog post "GitHub Actions: Transitioning from Node 16 to Node 20" by GitHub, I noticed this action is still running on node16.

This is the warning I see every time I my workflow:

Node.js 16 actions are deprecated. Please update the following actions to use Node.js 20: SvanBoxel/delete-merged-branch@main. For more information see: https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/.

[zangbe]

@SvanBoxel