unknown signature: percentile_cont_impl(decimal, decimal)

```
> show columns from transactions;
column_name | data_type | is_nullable | column_default | generation_expression | indices | is_hidden
--------------+-------------+-------------+----------------+-----------------------+---------------------+------------
id | INT8 | f | unique_rowid() | | {transactions_pkey} | f
amount | DECIMAL | t | NULL | | {transactions_pkey} | f
created_at | TIMESTAMPTZ | t | now() | | {transactions_pkey} | f
(3 rows)
```

```
> SELECT PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY amount ASC) FROM transactions;
ERROR: unknown signature: percentile_cont_impl(decimal, decimal)
SQLSTATE: 42883
```

**Environment:**
- CockroachDB Cloud Serverless

Jira issue: CRDB-29532

Epic CRDB-2474