ci: fixes missing phpunit version

Author: nunomaduro

.github/workflows/test.yaml

@@ -15,6 +15,10 @@ jobs:
                 dependency-version: [prefer-lowest, prefer-stable]
                 composer-version: [ v2 ]
                 include:
+                    -   php: '8.4'
+                        phpunit: '^12.0'
+                    -   php: '8.3'
+                        phpunit: '^12.0'
                     -   php: '8.3'
                         phpunit: '^12.0'
                     -   php: '8.2'