Fix deprecations (#4636)

* Fix PHP 8.4 deprecation

Implicitly marking parameter as nullable is deprecated, the explicit nullable type must be used instead

* [github workflow] Add additional php versions

caches/FileCache.php

@@ -45,7 +45,7 @@ class FileCache implements CacheInterface
         return $default;
     }
 
-    public function set($key, $value, int $ttl = null): void
+    public function set($key, $value, ?int $ttl = null): void
     {
         $item = [
             'key'           => $key,