⬆️ Upgrade Python package dependencies

[ebouchut]

Upgrade:

• mkdocs to version 1.4.2 (from 1.3.0).
• mkdocs-material to version 9.1.5 (from 7.3.6)

[ebouchut]

ℹ️ Here is how to upgrade locally:

# Uninstall all previously installed packages
# python -m pip freeze --exclude-editable | xargs python -m pip  uninstall -y

# Install the required packages
python -m pip install -r requirements.txt