ClickHouse dialect should not require interval qualifier

When the `require_interval_qualifier` dialect option was added (https://github.com/apache/datafusion-sqlparser-rs/pull/1398), the main concern was PostgreSQL. Modern clickhouse supports all of:

unquoted intervals

```
SELECT INTERVAL 1 DAY;

┌─toIntervalDay(1)─┐
1. │ 1 │
└──────────────────┘
```

quoted intervals

```
SELECT INTERVAL '1 d';

┌─toIntervalDay(1)─┐
1. │ 1 │
└──────────────────┘
```

Mixed intervals

```
SELECT INTERVAL '1 2:3:4' DAY TO SECOND;

┌─(toIntervalDay(1), toIntervalHour(2), toIntervalMinute(3), toIntervalSecond(4))─┐
1. │ (1,2,3,4) │
└─────────────────────────────────────────────────────────────────────────────────┘
```

---

The fix should be as simple as flipping one boolean [here](https://github.com/apache/datafusion-sqlparser-rs/blob/bf1741bee2acb8013660de21d314533fe5686e93/src/dialect/clickhouse.rs#L47-L49)

Open src/dialect/clickhouse.rs at the require_interval_qualifier setting and inspect the existing boolean. Adjust that setting so ClickHouse accepts unquoted, quoted, and mixed intervals as shown in the issue; done means those three examples no longer require an interval qualifier.

Written by the indexing model from the issue text.