Bump cibuildwheel in CI (#208)

Author: jrbourbeau

.github/workflows/wheels.yml

@@ -166,7 +166,7 @@ jobs:
         with:
           python-version: "3.x"
       - name: Build wheels
-        uses: pypa/cibuildwheel@v2.16.2
+        uses: pypa/cibuildwheel@v2.21.1
         env:
           CIBW_BUILD: ${{ matrix.build }}
           CIBW_ARCHS: ${{ matrix.arch }}