Fix regression ext.php (#7499)

fix https://github.com/FreshRSS/FreshRSS/issues/7498
Regression from https://github.com/FreshRSS/FreshRSS/pull/7495

p/ext.php

@@ -1,6 +1,7 @@
 <?php
 declare(strict_types=1);
 require(__DIR__ . '/../constants.php');
+require(LIB_PATH . '/lib_rss.php');	//Includes class autoloader
 
 function get_absolute_filename(string $file_name): string {
 	$core_extension = realpath(CORE_EXTENSIONS_PATH . '/' . $file_name);