fix missing import of container for resolving the queue connection from ioc

src/Queue/QueueServiceProvider.php

@@ -45,7 +45,7 @@ class QueueServiceProvider extends AbstractServiceProvider
         // Register a simple connection factory that always returns the same
         // connection, as that is enough for our purposes.
         $this->container->singleton(Factory::class, function (Container $container) {
-            return new QueueFactory(function () {
+            return new QueueFactory(function () use ($container) {
                 return $container->make('flarum.queue.connection');
             });
         });