Long story short, we haven't implemented a recursive (or folder) delete. This topic is covered in another post: FirebaseStorage: How to Delete Directory
For now, we recommend storing a list of files in another source (like the Realtime Database) and deleting files as necessary. You can also perform this type of delete in the Firebase Console (console.firebase.google.com).
In the future, we may offer this sort of functionality, but don't have it fully spec'ed out.
