Tests/RulesetInclusion: fix reference to old repo

Follow up to 1

Author: jrfnl

tests/Core/Ruleset/RuleInclusionTest.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0"?>
-<ruleset xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" name="RuleInclusionTest" xsi:noNamespaceSchemaLocation="https://raw.githubusercontent.com/squizlabs/PHP_CodeSniffer/master/phpcs.xsd">
+<ruleset xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" name="RuleInclusionTest" xsi:noNamespaceSchemaLocation="https://raw.githubusercontent.com/PHPCSStandards/PHP_CodeSniffer/master/phpcs.xsd">
 
     <rule ref="PSR2">
         <properties>