python versions need to be quoted

.github/workflows/build-docs.yml

@@ -21,7 +21,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v4
         with:
-          python-version: 3.10
+          python-version: '3.10'
 
       - name: Install dependencies
         run: pip install -r docs/requirements.txt