refactor(security): replace generic event with severity enum

Signed-off-by: Sebastian Krupinski <krupinski01@gmail.com>

core/lib/Security/Event/AuthenticationSucceededEvent.php

@@ -63,8 +63,8 @@ final class AuthenticationSucceededEvent extends Event implements SecurityReques
         return null;
     }
 
-    public function getSeverity(): int
+    public function getSeverity(): SecurityEventSeverity
     {
-        return SecurityEvent::SEVERITY_INFO;
+        return SecurityEventSeverity::INFO;
     }
 }