chore: tweak rector parallel config

Author: kenjis

rector.php

@@ -59,7 +59,7 @@
         PHPUnitSetList::PHPUNIT_100,
     ]);
 
-    $rectorConfig->parallel(120, 8, 15);
+    $rectorConfig->parallel(120, 8, 10);
 
     // paths to refactor; solid alternative to CLI arguments
     $rectorConfig->paths([__DIR__ . '/app', __DIR__ . '/system', __DIR__ . '/tests', __DIR__ . '/utils']);