refactor(security): replace generic event with severity enum

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

core/lib/Security/Event/SuspiciousActivityEvent.php

@@ -93,8 +93,8 @@ final class SuspiciousActivityEvent extends Event implements SecurityRequestEven
         return $this->reason;
     }
 
-    public function getSeverity(): int
+    public function getSeverity(): SecurityEventSeverity
     {
-        return SecurityEvent::SEVERITY_ERROR;
+        return SecurityEventSeverity::ERROR;
     }
 }