Don't show lists a book is already on in add form

bookwyrm/views/books/books.py

@@ -83,6 +83,7 @@ class Book(View):
         }
 
         if request.user.is_authenticated:
+            data["list_options"] = request.user.list_set.exclude(id__in=data["lists"])
             data["file_link_form"] = forms.FileLinkForm()
             readthroughs = models.ReadThrough.objects.filter(
                 user=request.user,