Add more return types after fixing a typo in my script

Author: nicolas-grekas

Tests/WorkflowTest.php

@@ -601,7 +601,7 @@ public function getListeners($eventName = null): array
     {
     }
 
-    public function getListenerPriority($eventName, $listener)
+    public function getListenerPriority($eventName, $listener): ?int
     {
     }