Replaced flake8 and isort with ruff #467

Job	Run time
Lint (black)	24s
Check for news fragments in 'changelog.d/'	8s
Test Python 3.8, Django 3.2, Redis.py latest	2m 13s
Lint (ruff)	25s
Test Python 3.8, Django 4.0, Redis.py latest	2m 18s
Lint (mypy)	30s
Test Python 3.8, Django 4.1, Redis.py latest	2m 19s
Test Python 3.8, Django 4.2, Redis.py latest	2m 26s
Test Python 3.9, Django 3.2, Redis.py latest	2m 11s
Test Python 3.9, Django 4.0, Redis.py latest	2m 18s
Test Python 3.9, Django 4.1, Redis.py latest	2m 15s
Test Python 3.9, Django 4.2, Redis.py latest	2m 24s
Test Python 3.10, Django 3.2, Redis.py latest	2m 15s
Test Python 3.10, Django 4.0, Redis.py latest	2m 15s
Test Python 3.10, Django 4.1, Redis.py latest	2m 5s
Test Python 3.10, Django 4.2, Redis.py latest	2m 26s
Test Python 3.6, Django 3.2, Redis.py latest	2m 32s
Test Python 3.7, Django 3.2, Redis.py latest	2m 22s
Test Python 3.11, Django 4.1, Redis.py latest	2m 14s
Test Python 3.11, Django 4.2, Redis.py latest	2m 24s
Test Python 3.11, Django 4.2, Redis.py master	2m 12s
Test Python 3.11, Django main, Redis.py latest	2m 18s
Test Python 3.11, Django main, Redis.py master	2m 36s
	45m 30s

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