Issue on docs leading-hint

- Page Link: https://doris.apache.org/zh-CN/docs/query-acceleration/hints/leading-hint#%E6%A1%88%E4%BE%8B

- Version: 2.1

- Reason: There is no difference in the execution plan before and after using the hint.（使用hint前后的执行计划没有区别，我理解这里想给读者呈现的内容是：使用hint后，plan会发生变化)

- Suggest: 我建议改为如下案例（我已经在本地的2.1.6环境验证）

第一步，建库表，并写入测试数据

```sql
CREATE DATABASE testleading;
USE testleading;

create table t1 (c1 int, c11 int) distributed by hash(c1) buckets 3 properties('replication_num' = '1');
create table t2 (c2 int, c22 int) distributed by hash(c2) buckets 3 properties('replication_num' = '1');
insert into t1 VALUES (1, 25), (2, 35), (3, 28), (4, 60), (5, 17);
insert into t2 VALUES (1, 25), (2, 35), (3, 28), (4, 60), (5, 17);
```

第二步，使用Hint前plan如下，t2表进行distribute，t1表不shuffle

```sql
explain shape plan select * from t1 join t2 on t1.c1 = c2;

Explain String
Planner: Nereids Planner
PhysicalResultSink
--PhysicalDistribute[DistributionSpecGather]
----hashJoin[INNER_JOIN] hashCondition=((t1.c1 = t2.c2)) otherCondition=()
------PhysicalOlapScan[t1]
------PhysicalDistribute[DistributionSpecHash]
--------PhysicalOlapScan[t2]
```

第三步，使用hint后plan如下，t1和t2表的执行计划相反，t1表进行distribute，t2表不shuffle

```sql
explain shape plan select /*+ leading(t2 t1) */ * from t1 join t2 on c1 = c2;

Explain String
Planner: Nereids Planner
PhysicalResultSink
--PhysicalDistribute[DistributionSpecGather]
----hashJoin[INNER_JOIN] hashCondition=((t1.c1 = t2.c2)) otherCondition=()
------PhysicalOlapScan[t2]
------PhysicalDistribute[DistributionSpecHash]
--------PhysicalOlapScan[t1]
Hint log:
Used: leading(t2 t1 )
UnUsed:
SyntaxError:
```

- May I contribute to this pull request? Our company has been frequently using Doris lately. If given the chance, I would also like to gradually become involved in the community.（如果确认该Issue的话，可以由我来提交PR吗，我很希望参与到doris社区当中）

- ScreenShot: