refactor: remove forum and topic feature chains

tools/audit-admin-contracts.php

@@ -52,7 +52,6 @@ function collect_php_schema_sections(string $themeRoot): array {
         'extensions'   => $themeRoot . '/src/Admin/Schema/SchemaExtensions.php',
         'tools'        => $themeRoot . '/src/Admin/Schema/SchemaTools.php',
         'shop'         => $themeRoot . '/src/Admin/Schema/SchemaShop.php',
-        'forum'        => $themeRoot . '/src/Admin/Schema/SchemaForum.php',
     ];
 
     foreach ($primary as $domain => $file) {