refactor: ES2021 features (#6540)

Co-authored-by: Antonio Román <kyradiscord@gmail.com>
Co-authored-by: Voltrex <mohammadkeyvanzade94@gmail.com>

test/shard.js

@@ -28,7 +28,7 @@ client.on('ready', () => {
     setTimeout(() => {
       console.log('kek dying');
       client.destroy();
-    }, 5000);
+    }, 5_000);
   }
 });