GH workflow: add Python 3.11

.github/workflows/integration.yml

@@ -13,7 +13,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-20.04]
-        python-version:  ["3.7", "3.8", "3.9", "3.10"]
+        python-version:  ["3.7", "3.8", "3.9", "3.10", "3.11"]
     steps:
     - name: Checkout
       uses: actions/checkout@v2