Revert "do not test against php 8.4"

This reverts commit 22d411f.

Author: Baptouuuu

.github/workflows/ci.yml

@@ -8,7 +8,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macOS-latest]
-        php-version: ['8.5']
+        php-version: ['8.4', '8.5']
         dependencies: ['lowest', 'highest']
     name: 'PHPUnit'
     steps: