ci: bump docker/setup-qemu-action from 3.7.0 to 4.2.0 - #13

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@11d5960a326750d5838078e36cf38b85af677262, docker/build-push-action@10e90e3645eae34f1e60eeb005ba3a3d33f178e8, docker/setup-buildx-action@8d2750c68a42422c14e847fe6c8ac0403b4cbd6f. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/