Ensure workflows use the latest versions of actions that are running on Node 20

[fornfrey]

Node 16 has reached its end of life, and GitHub initiated its deprecation process in the end of 2023. Actions running on Node 16 may no longer work in the future.

Curerntly, the trigger-argo-workflow
GitHub action produces the following warning:

Node.js 16 actions are deprecated. Please update the following actions to use Node.js 20: 
actions/cache/[email protected], actions/[email protected], google-github-actions/auth@v1,
hashicorp/vault-action@v2. For more information see: 
https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/.

• Actions in the repository should be updated to run on Node 20
• Third-party actions used in the workflows should be updated to the latest versions running on Node 20.