Deprecated Node.js actions

Stream: mathlib4

[Yaël Dillies]

Our CI actions are apparently deprecated. See eg this run:

Node.js 16 actions are deprecated. Please update the following actions to use Node.js 20: styfle/cancel-workflow-action@0.11.0. For more information see: https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/.

[Mario Carneiro]

#10155

[Notification Bot]

15 messages were moved from this topic to #mathlib4 > website GHA CI recommendation by Mario Carneiro.