build: use 3.12 to build

Author: alvarolopez

.github/workflows/packaging.yml

@@ -79,10 +79,10 @@ jobs:
       - test
       - build-sdist
     steps:
-      - name: Set up Python 3.13
+      - name: Set up Python 3.12
         uses: actions/setup-python@v5
         with:
-          python-version: 3.13
+          python-version: 3.12
 
       - name: Get cASO repo
         uses: actions/checkout@v4