Update Python versions tested

Author: StevenMaude

.github/workflows/ci-build.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python: [2.7, 3.5, 3.6, 3.7, 3.8]
+        python: ['3.7', '3.8', '3.9', '3.10']
 
     steps:
       - name: Checkout code