Update sphinx.yml

Author: Andrei

.github/workflows/sphinx.yml

@@ -15,7 +15,10 @@ jobs:
 
     steps:
       - uses: actions/checkout@v4
-      - uses: actions/setup-python@v4
+      - name: Set up Python 3.11
+        uses: actions/setup-python@v4
+        with:
+          python-version: 3.11.6
 
       - name: Build docs requirements
         run: pip install -r docs/requirements.txt