ci: bump pypa/cibuildwheel from 2.20 to 2.21 in the actions group

Bumps the actions group with 1 update: [pypa/cibuildwheel](https://github.com/pypa/cibuildwheel).


Updates `pypa/cibuildwheel` from 2.20 to 2.21
- [Release notes](https://github.com/pypa/cibuildwheel/releases)
- [Changelog](https://github.com/pypa/cibuildwheel/blob/main/docs/changelog.md)
- [Commits](pypa/cibuildwheel@v2.20...v2.21)

---
updated-dependencies:
- dependency-name: pypa/cibuildwheel
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: actions
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/pypi.yml

@@ -49,7 +49,7 @@ jobs:
         with:
           platforms: ${{matrix.qemu_arch}}
       - name: Build wheels
-        uses: pypa/cibuildwheel@v2.20
+        uses: pypa/cibuildwheel@v2.21
         env:
           CIBW_ARCHS: ${{matrix.cibw_arch}}
           CIBW_SKIP: "pp* cp313-*"