fix: review

Author: NelinD

src/Message.php

@@ -1,7 +1,6 @@
 <?php
 namespace sngrl\PhpFirebaseCloudMessaging;
 
-use ReturnTypeWillChange;
 use sngrl\PhpFirebaseCloudMessaging\Recipient\Recipient;
 use sngrl\PhpFirebaseCloudMessaging\Recipient\Topic;
 use sngrl\PhpFirebaseCloudMessaging\Recipient\Device;
@@ -152,7 +151,7 @@ public function setTimeToLive($value)
         return $this;
     }
 
-    #[ReturnTypeWillChange]
+    #[\ReturnTypeWillChange]
     public function jsonSerialize()
     {
         $jsonData = $this->jsonData;