Update Python version to 3.13 in deploy workflow - #207

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4, actions/setup-python@v5. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

Summary report available at: https://github.com/OSIPI/osipi.github.io/actions/runs/40889946662#summary-123503692983