fixed code test file after review

Author: Iamwade

testData/inspections/xml/PreferenceDeclarationInspection/classAttrForDoesNotExists/di.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0"?>
 <config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
-    <preference for="" type="Not\Existent\Class"/>
+    <preference for="Not\Existent\Class" type=""/>
 </config>