[Docs] Update Community Plugins page: rabbitmq_delayed_message_exchange is now archived

### Is your feature request related to a problem? Please describe. I noticed that the rabbitmq_delayed_message_exchange plugin is still listed as an active/maintained plugin on the [Community Plugins page](https://www.rabbitmq.com/community-plugins) and referenced in various delayed messaging guides. However, the repository was archived on Jan 29, 2026 and is now read-only: https://github.com/rabbitmq/rabbitmq-delayed-message-exchange Location of stale documentation: https://www.rabbitmq.com/community-plugins (If applicable) https://www.rabbitmq.com/blog/2015/04/16/scheduling-messages-with-rabbitmq/ ### Describe the solution you'd like Please update the documentation to mark this plugin as Archived/Deprecated. Given that RabbitMQ 4.0 has removed Mirrored Classic Queues (forcing Quorum Queues), and this plugin was the primary workaround for delayed messages, users need clear guidance on whether a native alternative exists or if we should be moving to external schedulers entirely. ### Describe alternatives you've considered _No response_ ### Additional context _No response_