Galaxy creates a control queue for each of its processes, but might not be cleaning them up properly despite setting auto_delete=True in the related code.
They can be manually cleaned up using aws sqs list-queues --output text | grep control | cut -f 2 | xargs -i aws sqs delete-queue --queue-url {} --output text but this will clobber the currently active processes queue too. This may require restarting the app.
See galaxyproject/galaxy#14647