[doc] explode-bitmap (4.x/3.x/2.1): stray explode_json_object example references non-existent columns; dev already dropped it

On the `EXPLODE_BITMAP` page (`sql-manual/sql-functions/table-functions/explode-bitmap.md`) in **version-4.x / version-3.x / version-2.1**, the last example is a copy-paste error:

```sql
CREATE TABLE example ( k1 INT, v1 bitmap ) ... ;
insert into example values(1,to_bitmap('10101')),(2,to_bitmap('0')),(3,to_bitmap(NULL));

SELECT id, k, v
FROM example
LATERAL VIEW explode_json_object(value_json) exploded_table AS k , v;
```
- It calls `explode_json_object(value_json)`, but `example` has no `value_json` column (only `k1`, `v1`), and selects `id, k, v` which don't exist either.
- The printed output (`k1` / `bit` columns: `2→0`, `1→10101`) is actually the result of **`explode_bitmap(v1)`**, not `explode_json_object`.
- On 2.1/3.x this fails (the `AS k, v` alias list is misparsed → `Unknown table 'v'`).

The **dev** version of this page has already removed this broken block. Recommend aligning 4.x/3.x/2.1 with dev — either drop the stray example or rewrite it as a valid `explode_bitmap(v1)` example matching the shown output. Happy to send the PR.