I had a friend go a little nuts sharing notes with me on a variety of topics. He's since unshared several of them, but they still show up in my list of notes shared with me. I can't access them, but I can still see that they are in my list. I can't get rid of them and they are making it more difficult to see the notes that I still do have access to. We've both synced multiple times. What can I do?