Bump Python version

[vitormattos]

Now we have two places that the Python version is locked:

• .docker/sphinx/Dockerfile
• .github/workflows/deploy.yml

Is necessary

• identify what's the latest Python version that Sphinx
• Bump the Python version at this project
• Define a way to make more easy to bump the Python version and Sphinx version when newest version is released
  Maybe using Dependabot