Regenerate client test cert, current one expires in 2032 - #1353

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: edgedb/action-release/validate-pr@master. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/