Upgrade GitHub Actions to checkout@v5 and setup-go@v6

[MamunC0der]

uses: actions/checkout@v4 → uses: actions/checkout@v5

uses: actions/setup-go@v5 → uses: actions/setup-go@v6

Reason:
Both actions include major updates that enhance security, caching efficiency, and Go environment setup performance.

Checkout v5 release notes:https://github.com/actions/checkout/releases/tag/v5.0.0
Setup-go v6 release notes:https://github.com/actions/setup-go/releases/tag/v6.0.0

[s1na]

Hi, thanks a lot for your contribution! 🙏
At the moment, the go-ethereum team is overloaded with pull requests and in order to ensure we can give high quality review and attention to critical changes, we are not accepting refactoring-only PRs or minor upgrades.

We really appreciate the effort and encourage you to keep contributing, but for now we need to focus our limited review bandwidth on feature work, bug fixes, and protocol changes.

Thanks for understanding!