build docs with python 3.12

.github/workflows/build.yml

@@ -51,10 +51,10 @@ jobs:
       uses: actions/checkout@v4
       with:
         persist-credentials: false
-    - name: Set up Python 3.9
+    - name: Set up Python 3.12
       uses: actions/setup-python@v4
       with:
-        python-version: '3.9'
+        python-version: '3.12'
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip