Normally, we'd use the delete_columns function to remove the old
`short_channel_id` string field, *but* we can't do that for sqlite, as
there are other tables with references to it. So add a FIXME to do
it once everyone has upgraded to an sqlite3 which has native support
for column deletion.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2752e04f8f