GHA uses "3.12" for Python 3.12 (#64)

Author: vstinner

.github/workflows/build.yml

@@ -16,6 +16,10 @@ jobs:
         #
         # Available Python versions: can be found here:
         # https://raw.githubusercontent.com/actions/python-versions/main/versions-manifest.json
+        #
+        # Allow pre-releases:
+        # https://github.com/actions/setup-python/blob/main/docs/advanced-usage.md#allow-pre-releases
+        # See "allow-prereleases: true" below.
         os: [ubuntu-latest]
         python:
           # CPython
@@ -26,7 +30,7 @@ jobs:
           - "3.11"
           # CPython 3.12 final is scheduled for October 2013:
           # https://peps.python.org/pep-0693/
-          - "3.12-dev"
+          - "3.12"
           # PyPy
           - "pypy2.7"
           - "pypy3.6"
@@ -60,6 +64,7 @@ jobs:
         uses: actions/setup-python@v4
         with:
           python-version: ${{ matrix.python }}
+          allow-prereleases: true
       - name: Install setuptools
         run: python -m pip install setuptools
       - name: Display the Python version