refactor: use $wgMetaNamespace variable

Author: harshkhandeparkar

mediawiki/LocalSettings.php

@@ -244,7 +244,7 @@
 
 $wgVisualEditorAvailableNamespaces = [
   "Help" => true,
-  "Metakgp" => true,
+  $wgMetaNamespace => true,
   "Template" => true,
 ];