Ruleset: update schema URL (#353)

PHPCS now offers permalinks for the schema.

Refs:
* PHPCSStandards/PHP_CodeSniffer 1094
* https://github.com/PHPCSStandards/schema.phpcodesniffer.com

Co-authored-by: jrfnl <jrfnl@users.noreply.github.com>

Author: jrfnl

VariableAnalysis/ruleset.xml

@@ -1,4 +1,4 @@
 <?xml version="1.0"?>
-<ruleset xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" name="VariableAnalysis" xsi:noNamespaceSchemaLocation="https://raw.githubusercontent.com/phpcsstandards/PHP_CodeSniffer/master/phpcs.xsd">
+<ruleset xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" name="VariableAnalysis" xsi:noNamespaceSchemaLocation="https://schema.phpcodesniffer.com/phpcs.xsd">
     <description>Plugin for PHP_CodeSniffer static analysis tool that adds analysis of problematic variable use.</description>
 </ruleset>