chore(ci): update PR actions to node16

[aali309]

Welcome to Cryostat! 👋

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---

Fixes: #1641

Description of the change:

This change updates the node version from 12 that is deprecated to v16 by updating actions/checkout@v2 to v4

Motivation for the change:

This change is helpful because it will get rid of the warning when running PR workflows because node12 is deprecated

How to manually test:

1. Run CRYOSTAT_IMAGE=quay.io... sh smoketest.sh...
2. ...

[andrewazores]

@aali309 is this meant to be a draft still or ready?

[aali309]

@aali309 is this meant to be a draft still or ready?

was just reading something to make sure, but it looks like its ready I think, main thing needed was to change the actions/checkout

[andrewazores]

https://github.com/cryostatio/cryostat/actions/runs/6266876246

[tthvo]

Well Node 20 is coming this Spring 2024: https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/