update tests to have max variable

Author: lachiebol

.github/workflows/matomo-tests.yml

@@ -37,7 +37,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php: [ '7.4', '8.4' ]
+        php: [ '7.4', 'matomo5_max_php' ]
         target: ['minimum_required_matomo', 'maximum_supported_matomo']
     steps:
       - uses: actions/checkout@v3