bump symfony to 5.4.21

adapt to the new EventDispatcher API
  - Symfony\Component\EventDispatcher => Symfony\Contracts\EventDispatcher
  - dispatch() arguments swap
  - execute() must return int

cli

@@ -2,7 +2,7 @@
 <?php
 
 use Symfony\Component\Console\Input\ArgvInput;
-use Symfony\Component\EventDispatcher\Event;
+use Symfony\Contracts\EventDispatcher\Event;
 
 if (php_sapi_name() !== 'cli') {
     echo 'This script run only from the command line'.PHP_EOL;
@@ -15,7 +15,7 @@ try {
     $input = new ArgvInput();
 
     if (! in_array($input->getFirstArgument(), ['db:migrate', 'db:version'])) {
-        $container['dispatcher']->dispatch('app.bootstrap', new Event);
+        $container['dispatcher']->dispatch(new Event, 'app.bootstrap');
     }
 
     $container['cli']->run($input);