Fixed doc publishing

The github action to do this was still based on py3.6
but the latest changes on tox.ini requires a newer version
of tox which doesn't exist for py3.6. Thus run the workflow
on a newer python version

.github/workflows/ci-publish-pages.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-20.04
     strategy:
       matrix:
-        python-version: [3.6]
+        python-version: [3.10]
 
     steps:
     - uses: actions/checkout@v2