pin python version for doc building

Author: jepler

.github/workflows/build.yml

@@ -220,7 +220,7 @@ jobs:
     - name: Set up Python 3
       uses: actions/setup-python@v2
       with:
-        python-version: "3.x"
+        python-version: "3.10.6"
     - name: Install dependencies
       run: |
         sudo apt-get update