Drop Python v3.7 support

Date when Python project won’t support v3.7

• Python 3.7 support will be dropped in June 27th of 2023
• Platform which still uses Py3.7

Todos

DuniterPy

• Bump minimum version in pyproject.toml
• Delete test job for v3.7 from .gitlab-ci.yml
• Upgrade pyupgrade to --py38-plus argument in pre-commit hook
• Update minimal version in documentation: README.md and docs/index.rst

Container

• Delete v3.7 Docker image generation: Drop Py3.7 image generation (docker/python3/poetry#9 - closed)

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• Create ticket for Py3.8: Drop Python v3.8 support (#199 - closed)