Fix type overrides

See https://github.com/kyleconroy/sqlc/issues/819

postgres/transactions.sql.go

@@ -60,7 +60,7 @@ type GetTransactionsForAccountRow struct {
 	ID      uuid.UUID
 	Date    time.Time
 	Memo    string
-	Amount  postgres.Numeric
+	Amount  Numeric
 	Account string
 	Payee   string
 }