To retire a bundle, you go here:
https://leanpub.com/author_dashboard/bundles/published
If a bundle has been published, you will see a "Retire" option, like in this screenshot:

To retire a bundle, you go here:
https://leanpub.com/author_dashboard/bundles/published
If a bundle has been published, you will see a "Retire" option, like in this screenshot: