chore: update actions in GitHub Actions workflows

[striezel]

The following updates are performed:

• update actions/checkout to v4
• update actions/setup-node to v4
• update pnpm/action-setup to v3

Still using the outdated actions will generate several warnings in CI runs, for example in https://github.com/TooTallNate/proxy-agents/actions/runs/7876212832:

Node.js 16 actions are deprecated. Please update the following actions to use Node.js 20: actions/checkout@v3, pnpm/action-setup@v2, actions/setup-node@v3. For more information see: https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/.

The PR will get rid of those warnings.

[changeset-bot[bot]]

⚠️ No Changeset found

Latest commit: 02ba795371e63b62b5bbdff818aa35d300838f91

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

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Name	Status	Preview	Updated (UTC)
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[TooTallNate]

Thanks!