deps(python/biometric-engine): bump prometheus-client from 0.21.1 to 0.26.0 in /services/biometric-engine - #171

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/github-script@v7, actions/upload-artifact@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/