Document how to undo git-crypt, e.g. remove item from .gitattributes

There is documentation about how to apply git-crypt, but nothing to un-apply it. What happens when a file that is encrypted, with an entry in the .gitattributes file to use the git-crypt filters, and a new commit removes the .gitattributes entry? How is a file intentionally released from git-crypt filters?