chore: Update PHP versions in CI

Author: bastianallgeier

.github/workflows/ci.yml

@@ -9,7 +9,7 @@ jobs:
     timeout-minutes: 5
     strategy:
       matrix:
-        php: ["8.1", "8.2", "8.3"]
+        php: ["8.2", "8.3", "8.4"]
     env:
       extensions: mbstring, pcov
       ini: pcov.directory=., "pcov.exclude=\"~(vendor|tests)~\""