Update phpunit.xml

Author: canvural

phpunit.xml

@@ -1,7 +1,7 @@
 <?xml version="1.0"?>
 <phpunit
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-    xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.3/phpunit.xsd"
+    xsi:noNamespaceSchemaLocation="./vendor/phpunit/phpunit/phpunit.xsd"
     beStrictAboutChangesToGlobalState="true"
     beStrictAboutCoversAnnotation="true"
     beStrictAboutOutputDuringTests="true"