Switched to Debian Bullseye for idf-python-wheels-legacy image

[jakub-kocka]

Description

This change is needed because of the version of Python.

Related

Testing

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Checklist

Before submitting a Pull Request, please ensure the following:

• 🚨 This PR does not introduce breaking changes.
• All CI checks (GH Actions) pass.
• Documentation is updated as needed.
• Tests are updated or added as necessary.
• Code is well-commented, especially in complex areas.
• Git history is clean — commits are squashed to the minimum necessary.

[peterdragun]

LGTM

[jakub-kocka]

Thank you for the review. I am merging this.