ci: avoid running setup.py directly for build

* Use "python -m build" instead of invoking setup.py directly.
* https://blog.ganssle.io/articles/2021/10/setup-py-deprecated.html

Author: GraemeWatt

.github/workflows/ci.yml

@@ -60,7 +60,7 @@ jobs:
         python-version: '3.12'
     - name: Build PyPI package
       run: |
-        pip install --upgrade pip setuptools wheel
-        python setup.py sdist bdist_wheel
+        pip install build
+        python -m build
     - name: Publish distribution to PyPI
       uses: pypa/gh-action-pypi-publish@release/v1