Smaller build matrix

Author: rhpvorderman

.github/workflows/ci.yml

@@ -81,7 +81,10 @@ jobs:
           - 3.7
           - 3.8
           - 3.9
-        os: ["macos-latest", "ubuntu-latest"]
+        os: ["ubuntu-latest"]
+        include:
+          - os: "macos-latest"
+            python-version: 3.8
     steps:
       - uses: actions/[email protected]
         with: