Drop MacOS from CI (#672)

Author: mk-mxp

.github/workflows/exercise-tests-phpunit-9.yml

@@ -16,7 +16,7 @@ jobs:
       fail-fast: false
       matrix:
         php-version: [8.0, 8.1, 8.2]
-        os: [ubuntu-22.04, windows-2022, macOS-12]
+        os: [ubuntu-22.04, windows-2022]
 
     steps:
       - name: Set git line endings