Add missing copyright

Author: manuelcanepa

app/code/Magento/Developer/Test/Unit/Model/XmlCatalog/Format/VsCodeTest.php

@@ -1,4 +1,8 @@
 <?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
 
 namespace Magento\Developer\Test\Unit\Model\XmlCatalog\Format;
 

app/code/Magento/Developer/Test/Unit/Model/XmlCatalog/Format/_files/invalid_catalog.xml

@@ -1,2 +1,8 @@
 <?xml version="1.0"?>
+<!--
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+-->
 <root />

app/code/Magento/Developer/Test/Unit/Model/XmlCatalog/Format/_files/valid_catalog.xml

@@ -1,4 +1,10 @@
 <?xml version="1.0"?>
+<!--
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+-->
 <catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog">
   <system systemId="urn:magento:framework:Acl/etc/acl.xsd" uri="../vendor/magento/framework/Acl/etc/acl.xsd"/>
   <system systemId="urn:magento:module:Magento_Store:etc/config.xsd" uri="../vendor/magento/module-store/etc/config.xsd"/>