Build on 3.9

Author: Padraig Gleeson

.github/workflows/build-ci.yml

@@ -13,7 +13,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: [ "3.8", "3.10" ]
+        python-version: [ "3.8", "3.9" ]
 
     steps:
     - uses: actions/checkout@v2