Cancels the deletion request for a folder. This method may be called on a folder in any state. If the folder is in the ACTIVE state the result will be a no-op success. In order to succeed, the folder's parent must be in the ACTIVE state. In addition, reintroducing the folder into the tree must not violate folder naming, height, and fanout constraints described in the CreateFolder documentation. The caller must have resourcemanager.folders.undelete permission on the identified folder.