Optimize parallelism

Author: heiglandreas

.github/workflows/actions.yml

@@ -22,12 +22,13 @@ jobs:
     runs-on: ubuntu-latest # ${{ matrix.operating-system }}
     continue-on-error: ${{ matrix.experimental }}
     strategy:
+      max-parallel: 2
       matrix:
         # operating-system: [ubuntu-latest, windows-latest, macos-latest]
-        php-versions: ['7.3', '7.4', '8.0']
+        php-versions: ['7.3', '7.4']
         experimental: [false]
         include:
-          - php-versions: '8.1'
+          - php-versions: ['8.0', '8.1']
             experimental: true
     name: PHP ${{ matrix.php-versions }} # Test on ${{ matrix.operating-system }}
     steps: