Test on ubuntu-latest, macos-latest, windows-latest

Author: hankcs

.github/workflows/unit-tests.yml

@@ -33,12 +33,6 @@ jobs:
             python-version: "3.7"
 
         include:
-          # GHA doesn't list 3.6 for ubuntu-22
-          - os: ubuntu-20.04
-            python-version: "3.6"
-          - os: ubuntu-20.04
-            python-version: "3.7"
-
           # MacOS 13 required for Python < 3.8
           - os: macos-13
             python-version: "3.6"