[MNT] Update pre-commit pyupgrade config

[MatthewMiddlehurst]

What does this implement/fix? Explain your changes.

Updates the pyupgrade configuration to drop Python 3.8, which we no longer support.

[aeon-actions-bot]

Thank you for contributing to aeon

I have added the following labels to this PR based on the title: [ $\color{#EC843A}{\textsf{maintenance}}$ ].

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If our pre-commit code quality check fails, any trivial fixes will automatically be pushed to your PR unless it is a draft.

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PR CI actions

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• Run pre-commit checks for all files
• Run all pytest tests and configurations
• Run all notebook example tests
• Run numba-disabled codecov tests
• Stop automatic pre-commit fixes (always disabled for drafts)
• Push an empty commit to re-run CI checks

[MatthewMiddlehurst]

ofcourse