PHPUnit config: minor tweak

Author: jrfnl

phpunit.xml.dist

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <phpunit
 	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-	xsi:noNamespaceSchemaLocation="http://schema.phpunit.de/7.5/phpunit.xsd"
+	xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/7.5/phpunit.xsd"
 		backupGlobals="true"
 		bootstrap="tests/bootstrap.php"
 		convertErrorsToExceptions="true"