Use ::class syntax to fetch class name instead of get_class() function (#3910)

extensions/package-manager/src/Api/Serializer/TaskSerializer.php

@@ -24,7 +24,7 @@ class TaskSerializer extends AbstractSerializer
     {
         if (! ($model instanceof Task)) {
             throw new InvalidArgumentException(
-                get_class($this).' can only serialize instances of '.Task::class
+                $this::class.' can only serialize instances of '.Task::class
             );
         }