doc bug: EXPORT_SET example output table has 6 columns but the SQL selects only 1

On the `EXPORT_SET` page (`sql-manual/sql-functions/scalar-functions/string-functions/export-set.md`, present in `version-4.x` and the dev/`current` docs), one example does not match its own output:

```sql
SELECT EXPORT_SET(`bits`, `on`, `off`, `sep`, `num_of_b`)
FROM `test_export_set`;
```

The SQL selects a **single** column (the `EXPORT_SET(...)` result), but the documented output table shows **six** columns: `bits | on | off | sep | num_of_b | ans`. So the displayed output cannot be produced by the shown query — running the query as written returns only the `ans` column.

The output table clearly intends to show the input columns alongside the result (the last column is even aliased `ans`). Suggested fix — align the SQL with the shown output:

```sql
SELECT `bits`, `on`, `off`, `sep`, `num_of_b`,
EXPORT_SET(`bits`, `on`, `off`, `sep`, `num_of_b`) AS ans
FROM `test_export_set`;
```

(EN + ZH, both `version-4.x` and dev/`current`.) Filing separately from the setup-data change for this page so the SQL/output correction can be reviewed on its own.