🧹 Simplify cibuildwheel v4 configuration

[burgholzer]

🤖 AI text below 🤖

Description

Simplify the cibuildwheel configuration after the reusable packaging workflow
moved to cibuildwheel v4:

• remove the unsupported cp313t-* skip selector;
• rely on cibuildwheel v4's built-in ABI3 audit instead of appending a duplicate
  audit to the repair command;
• remove the explicit manylinux_2_28 image settings and rely on cibuildwheel
  v4's matching defaults.

The generic cp3??t-* test skip remains because test dependencies do not yet
provide the required free-threaded wheels. Consequently, cp314t continues to
be built but is not tested in the wheel job.

The corresponding migration guidance is documented in
workflows#424.

Validation

• uvx --from cibuildwheel==4.1.0 cibuildwheel --platform macos --print-build-identifiers .
• uvx nox --non-interactive -s lint
• git diff --check

Checklist

• The pull request only contains commits that are focused and relevant to
  this change.
• Tests are not applicable to this build-configuration cleanup.
• Documentation, changelog, and upgrade-guide changes are not needed in
  this consumer repository; migration guidance lives in workflows#424.
• The changes follow the project's style guidelines and introduce no new
  warnings.
• The local validation checks pass.
• I have reviewed the proposed changes.

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