Bump cryptography from 44.0.0 to 50.0.0 in /sample-apps/flask-openai - #680

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/setup-python@v5, AikidoSec/firewall-tester-action@v1.0.15. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/