sqldb: use the new schema

We put this new schema update into the main line and change the
versions of the schema updates which are currently only available
in dev builds. The schemas need to be chronological therefore we
also need to rename the file numbers.

sqldb/sqlc/migrations/000007_invoice_add_settled_index.down.sql

@@ -0,0 +1 @@
+DROP INDEX IF EXISTS invoices_settle_index_idx;