Specify a python version for docs test

Author: rhpvorderman

.github/workflows/ci.yml

@@ -28,6 +28,10 @@ jobs:
   docs:
     needs: lint
     runs-on: ubuntu-20.04
+    strategy:
+      matrix:
+        python-version:
+          - 3.6
     steps:
       - uses: actions/[email protected]
       - name: Set up Python ${{ matrix.python-version }}