Use Python 3.9 as target version for Ruff & Black rules

[kaxil]

Since we dropped support of Python 3.8 (after it reach EOL), we missed changing rules for black & ruff.

For reviewers: easier to just review first commit, second commit is mostly autogen code

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Read the Pull Request Guidelines for more information.
In case of fundamental code changes, an Airflow Improvement Proposal (AIP) is needed.
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[jscheffl]

Interesting. How can it be that I over-looked the changes in the first commit when removing Python 3.9 support?