chore: github action version bumps

[erikburt]

What

Updating Github Action references in all workflows.

Why

Github Actions node16 deprecation. See blog post (github.blog)

Node16 has been out of support since September 2023. As a result we have started the deprecation process of Node16 for GitHub Actions. We plan to migrate all actions to run on Node20 by Spring 2024.
Following on from our warning in workflows using Node16 we will start enforcing the use of Node20 rather than Node16 on the 13th of May.

Notes

RE-2531

Outdated Dependency Paths:

[ERROR] Deprecated dependencies found (2)!!
contracts.yml -> test -> actions/checkout@v2 -> node12
contracts.yml -> test -> actions/setup-node@v2 -> node12

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Name	Status	Preview	Comments	Updated (UTC)
chainlink-prediction-game	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	May 9, 2024 5:04pm

[erikburt]

Very minor changes - going to merge.