ci(pypi): skip PyPy wheels (CIBW_SKIP=pp*)

The v1.1.0 release run failed because cibuildwheel by default builds
for both CPython and PyPy, and PyPy 3.8/3.9/3.10 don't have the
PyModule_GetFilenameObject and other C API symbols that pybind11
requires:

  /tmp/.../pybind11/pybind11.h:1652:28: error:
    'PyModule_GetFilenameObject' was not declared in this scope

CPython cp38 through cp313 all built successfully. PyPy support for
pybind11 is not a goal of this project, so skip the PyPy targets
entirely instead of trying to patch around upstream gaps.

Author: LimHyungTae

.github/workflows/pypi.yml

@@ -48,6 +48,10 @@ jobs:
       - name: Build all wheels
         if: github.event_name == 'release'
         uses: pypa/cibuildwheel@v2.21.3
+        env:
+          # PyPy lacks the C API symbols pybind11 needs (PyModule_GetFilenameObject etc.).
+          # Restrict to CPython only — PyPy native-extension support is not a goal here.
+          CIBW_SKIP: "pp*"
         with:
           package-dir: ${{github.workspace}}/python/