Bump pypa/cibuildwheel from 2.19.2 to 2.21.0

Bumps [pypa/cibuildwheel](https://github.com/pypa/cibuildwheel) from 2.19.2 to 2.21.0.
- [Release notes](https://github.com/pypa/cibuildwheel/releases)
- [Changelog](https://github.com/pypa/cibuildwheel/blob/main/docs/changelog.md)
- [Commits](pypa/cibuildwheel@v2.19.2...v2.21.0)

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

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

.github/workflows/cibuildwheel.yml

@@ -34,7 +34,7 @@ jobs:
         fetch-depth: 0
 
     - name: "Building ${{ matrix.os }} (${{ matrix.arch }}) wheels"
-      uses: pypa/cibuildwheel@v2.19.2
+      uses: pypa/cibuildwheel@v2.21.0
       env:
         # Skips pypy and musllinux for now.
         CIBW_SKIP: "pp* cp36-* cp37-* *-musllinux*"