ci: bump actions/checkout from 4.3.1 to 7.0.1 - #135

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/setup-go@40f1582b2485089dde7abd97c1529aa768e1baff, golangci/golangci-lint-action@9fae48acfc02a90574d7c304a1758ef9895495fa. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/