ci(pypi): explicitly set up python

.github/workflows/pypi.yml

@@ -12,6 +12,10 @@ jobs:
         uses: actions/checkout@v4
         with:
           submodules: true
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.11"
       - name: Build sources
         run: pipx run build -n -s
       - name: Upload sources