Comment 6 for bug 1904305

@Kovid: do you object to me changing annotation_count_for_book to:
        count = 0
        for (data,) in self.execute('SELECT annot_data FROM annotations WHERE book=?', (book_id,)):
            if '"removed": true' not in data:
                count += 1
        return count

I could unpack the json and check that but it seems that it takes time for no good reason.