add php8.4 to tests workflow matrix

Author: faissaloux

Diff for: .github/workflows/tests.yml

@@ -8,7 +8,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macos-latest]
-        php: ['8.1', '8.2', '8.3']
+        php: ['8.1', '8.2', '8.3', '8.4']
         pest: ['2.*', '3.*']
         dependency-version: [prefer-lowest, prefer-stable]
         exclude: