ci: bump actions/setup-go from 6 to 7 - #33

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: goreleaser/goreleaser-action@v6, mlugg/setup-zig@v1. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/