Remove superflous comment in rename_author

src/calibre/library/database2.py

@@ -2772,7 +2772,6 @@ def rename_author(self, old_id, new_name):
             self.set_author_sort(book_id, ss)
             # the caller will do a general refresh, so we don't need to
             # do one here
-        # Now delete the old author from the DB
         return new_id
 
     # end convenience methods