GitHub Actions: setup-python allow-prereleases for 3.12 (#12252)

Author: cclauss

.github/workflows/ci.yml

@@ -109,14 +109,14 @@ jobs:
           - "3.9"
           - "3.10"
           - "3.11"
-          - key: "3.12"
-            full: "3.12-dev"
+          - "3.12"
 
     steps:
       - uses: actions/checkout@v3
       - uses: actions/setup-python@v4
         with:
-          python-version: ${{ matrix.python.full || matrix.python }}
+          python-version: ${{ matrix.python }}
+          allow-prereleases: true
 
       - name: Install Ubuntu dependencies
         if: matrix.os == 'Ubuntu'