chore: remove unnecessary phpunit extension

phpunit.xml

@@ -18,8 +18,4 @@
             <directory suffix=".php">src</directory>
         </include>
     </source>
-    <extensions>
-        <bootstrap class="Distantmagic\Resonance\PHPUnitSwooleCoroutineExtension">
-        </bootstrap>
-    </extensions>
 </phpunit>

src/PHPUnitSwooleCoroutineExtension.php

-<?php
-
-declare(strict_types=1);
-
-namespace Distantmagic\Resonance;
-
-use PHPUnit\Event\TestRunner\Finished;
-use PHPUnit\Event\TestRunner\FinishedSubscriber;
-use PHPUnit\Runner\Extension\Extension;
-use PHPUnit\Runner\Extension\Facade as EventFacade;
-use PHPUnit\Runner\Extension\ParameterCollection;
-use PHPUnit\TextUI\Configuration\Configuration;
-use Swoole\Coroutine;
-use Swoole\Timer;
-
-final class PHPUnitSwooleCoroutineExtension implements Extension
-{
-    public function bootstrap(Configuration $configuration, EventFacade $facade, ParameterCollection $parameters): void
-    {
-        $facade->registerSubscriber(new class($this) implements FinishedSubscriber {
-            public function __construct(private PHPUnitSwooleCoroutineExtension $thisClass) {}
-
-            public function notify(Finished $event): void
-            {
-                $this->thisClass->executeAfterLastTest();
-            }
-        });
-    }
-
-    public function executeAfterLastTest(): void
-    {
-        /**
-         * @var array{ coroutine_num: int } $coroutineStats
-         */
-        $coroutineStats = Coroutine::stats();
-
-        while ($coroutineStats['coroutine_num'] > 1) {
-            Coroutine::sleep(0.1);
-        }
-
-        Timer::clearAll();
-    }
-}