You can't cancel terms of a license, Creative Commons, specific copyleft or strict copyright.
When you want that everyone doesn't use your work anymore, you become the only person who has got all rights on it.
In this case, contact an admin who will edit the title of the topic, set a "|retired|" tag and move it to a special category. The post will be edited to say that the author doesn't want that we use his/her work anymore.
When you want that everyone doesn't use your work anymore, you become the only person who has got all rights on it.
In this case, contact an admin who will edit the title of the topic, set a "|retired|" tag and move it to a special category. The post will be edited to say that the author doesn't want that we use his/her work anymore.