Update GHAs to use Node JS 20 instead of versions 16, 12

[SarahFrench]

Background

Currently GHA runs show warnings about actions using Node 12 and 16 - these versions aren't supported and we should upgrade to Node 20.

What kind of contribution is this issue about?

GHAs

Related PR(s), if any:

• https://github.com/GoogleCloudPlatform/magic-modules/actions/runs/8124429288

Details

• Node 12 will be forced to run on Node 16: https://github.blog/changelog/2022-09-22-github-actions-all-actions-will-begin-running-on-node16-instead-of-node12/
• Node 16 should be updated to Node 20 : https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/

[SarahFrench]

Note from triage: can reference actions by version/tag if it's an official actions action, otherwise use commits

[github-actions]

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