Cleanup quality
# What does this PR do?

This PR cleans up a couple of things after the big #21480 
- adds the ruff cache to gitignore just in case (that folders comes with its own auto-generated gitignore so shouldn't be necessary but better be safe)
- remove all mentions of flake8 and isort from the doc
- use the per file rules to enable back quality checks on all inits.
_The documentation is not available anymore as the PR was closed or merged._