chore(api): update dependency flake8 to v6 (develop)

This MR contains the following updates:

Package	Type	Update	Change
flake8 (changelog)	dev-dependencies	major	==3.9.2 -> ==6.0.0

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Release Notes

pycqa/flake8

v6.0.0

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v5.0.4

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v5.0.3

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v5.0.2

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v5.0.1

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v5.0.0

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v4.0.1

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v4.0.0

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Configuration

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