build: update checkout action to v5

[rejected-l]

Node 24 compatibility: switch all jobs to actions/checkout@v5. Requires runner v2.327.1+. Pure maintenance, behavior unchanged.

Ref: https://github.com/actions/checkout/releases/tag/v5.0.0

[github-actions]

Thank you for your contribution to the Solidity compiler! A team member will follow up shortly.

If you haven't read our contributing guidelines and our review checklist before, please do it now, this makes the reviewing process and accepting your contribution smoother.

If you have any questions or need our help, feel free to post them in the PR or talk to us directly on the #solidity-dev channel on Matrix.

[Daulox92]

Node 24 compatibility: switch all jobs to actions/checkout@v5. Requires runner v2.327.1+. Pure maintenance, behavior unchanged.

Ref: https://github.com/actions/checkout/releases/tag/v5.0.0

#16160

[r0qs]

Thanks for this contribution! We're actually handling all GitHub Actions updates together in #16200. Closing this PR since it will be covered there.