store: Drop the vid sequence with 'cascade'

Since it is used for the default value, we get an error

  sequence sgdNNN.<table>_vid_seq membership in
  replication set default depends on sequence sgdNNN.<table>_vid_seq

That makes all pruning by rebuilding tables fail

Author: lutter

store/postgres/src/relational/prune.rs

@@ -235,6 +235,7 @@ impl TablePair {
             )?;
         }
 
+        writeln!(query, "drop sequence {src_nsp}.{vid_seq} cascade;")?;
         writeln!(query, "drop table {src_qname};")?;
         writeln!(query, "alter table {dst_qname} set schema {src_nsp}")?;
         conn.transaction(|conn| conn.batch_execute(&query))?;