Drop Python 3.9 support (#4412)

* Drop Python 3.9 support

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* generate-workflows

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* fixes

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* remove extra reference to pypy310

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* changelog

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* fix flask tests

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* fix google-genai tests

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* fix google-genai tests

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* fix

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* remove unused _ensure_gzip_single_response

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Signed-off-by: emdneto <9735060+emdneto@users.noreply.github.com>
Co-authored-by: Riccardo Magliocchetti <riccardo.magliocchetti@gmail.com>