Cookiecutter - fix template and upgrade deps

[jbpenrath]

Bug Report

Problematic Behavior By updating funmooc, we encount several issues with new version of Django and Python. The modification made in fun mooc should be port in cookiecutter.

Environment

• Richie version: 2.26.0

Additional context/Screenshots

• https://github.com/openfun/fun-richie-site-factory/pull/209
• https://app.circleci.com/pipelines/github/openfun/richie/10181/workflows/d3723589-4664-4d81-98f0-756af08aa289/jobs/237494
• https://github.com/openfun/fun-richie-site-factory/pull/211