An error message from github actions

[gbregman]

When running our github actions there is following message for each action:

Node.js 16 actions are deprecated. Please update the following actions to use Node.js 20: andstor/file-existence-action@20b4d2e596410855db8f9ca21e96fbe18e12930b. For more information see: https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/.

It seems that we need to change the "Check coredump existence" step to use a later version.