CI: Run installation tests on Python 3.10

Author: effigies

.github/workflows/pythonpackage.yml

@@ -117,11 +117,11 @@ jobs:
         python-version: [3.7, 3.8, 3.9, "3.10"]
         install: [repo]
         include:
-          - python-version: 3
+          - python-version: "3.10"
             install: sdist
-          - python-version: 3
+          - python-version: "3.10"
             install: wheel
-          - python-version: 3
+          - python-version: "3.10"
             install: editable
 
     env: