Update GitHub Actions versions

[PixelPil0t1]

Update GitHub Actions versions

[landabaso]

Hey @junderw this looks good to me. It fixes the red CI runs (e.g. #2248 , #2247 ). I applied the same changes in my fork and the workflow went green: https://github.com/landabaso/bitcoinjs-lib/actions/runs/16500766519

main_ci.yml currently pins v2/v3 Actions to specific SHAs. Was there a particular reason (security/reproducibility)? If not, moving to the v4 tags (or pinning the latest v4 SHAs) seems fine. Once this merges, the failing workflows on master should pass again.

[junderw]

LGTM if we want to trust the repo maintainers of those actions.

Some users complained and I saw nothing wrong with pinning, so I allowed it.

This will probably upset those users.

I am indifferent.