- Bump actions/upload-artifact to v6, actions/setup-python to v6,
actions/checkout to v5, and docker/setup-qemu-action to v4 so all
actions run on Node 24 (Node 20 is deprecated on GitHub runners).
- Bump pypa/cibuildwheel to v3.4.1 so its bundled actions/setup-python
also runs on Node 24.
- Drop CIBW_SKIP=pp*: PyPy is no longer enabled by default in
cibuildwheel 3.x, so the selector matched nothing and triggered an
"Invalid skip selector" warning.
- Add CIBW_TEST_SKIP for cp38 macOS arm64 to silence the cibuildwheel
warning that the arm64 slice of cp38 universal2 wheels can't be tested
(the cp38 installer is x86_64-only).