Fix default class string for options resolver

src/Discord/Discord.php

@@ -1433,7 +1433,7 @@ protected function resolveOptions(array $options = []): array
                 'intents' => Intents::getDefaultIntents(),
                 'socket_options' => [],
                 'cache' => [AbstractRepository::class => null], // use LegacyCacheWrapper
-                'collection' => [Collection::class => null],
+                'collection' => Collection::class,
             ])
             ->setAllowedTypes('token', 'string')
             ->setAllowedTypes('logger', ['null', LoggerInterface::class])