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

app/Console/TaskTriggerCommand.php

@@ -16,7 +16,7 @@ class TaskTriggerCommand extends BaseCommand
             ->setDescription('Trigger scheduler event for all tasks');
     }
 
-    protected function execute(InputInterface $input, OutputInterface $output)
+    protected function execute(InputInterface $input, OutputInterface $output): int
     {
         foreach ($this->getProjectIds() as $project_id) {
             $tasks = $this->taskFinderModel->getAll($project_id);
@@ -27,6 +27,7 @@ class TaskTriggerCommand extends BaseCommand
                 $this->sendEvent($tasks, $project_id);
             }
         }
+        return 0;
     }
 
     private function getProjectIds()