⬆️ Upgrade dependencies (PyYAML and mkdocs-material)

[ebouchut]

This PR mainly updates the PyYAML dependency to fix an issue with Python 3.12 used by GitHub Actions since yesterday (2023-10-26) where the deploy workflow can fail when installing the project's required dependencies (in the Run pip install -r requirements.txt step):

Collecting PyYAML==6.0 (from -r requirements.txt (line 29))
Downloading PyYAML-6.0.tar.gz (124 kB)
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 125.0/125.0 kB 14.1 MB/s eta 0:00:00
Installing build dependencies: started
Installing build dependencies: finished with status 'done'
Getting requirements to build wheel: started
Getting requirements to build wheel: finished with status 'error'
error: subprocess-exited-with-error

✅ The solution is to upgrade PyYAML to 6.0.1 from 6.0 as suggested here