Fix syntax error in delete-old-data.sql

sql/delete-old-data.sql

@@ -1,5 +1,4 @@
 -- delete data older than one month. It's taking about 18 days to fill a gig, and we have
 -- 3 gig volume currently. That gives us 54 days. But 30 days is plenty and this gives us margin
 -- in case the rate of growth of data increases.
-delete from dataset join stories using id
-where timestamp <= unixepoch()-30*24*60*60
+delete from dataset join stories using (id) where timestamp <= unixepoch()-30*24*60*60