[Bug] get_json_string does not support array

### Search before asking

- [x] I had searched in the [issues](https://github.com/apache/doris/issues?q=is%3Aissue) and found no similar issues.

### Version

2.1.11 branch-2.1

### What's Wrong?

```plpgsql
SELECT get_json_string(
'[{"k1":"v1"}, {"k2":"v2"}, {"k1":"v3"}, {"k1":"v4"}]',
'$.k1'
);
```
I can run this sql in 2.1.10 version

but after upgrade version to 2.1.11 ,it run fail

### What You Expected?

just report this bug

### How to Reproduce?

_No response_

### Anything Else?

_No response_

### Are you willing to submit PR?

- [x] Yes I am willing to submit a PR!

### Code of Conduct

- [x] I agree to follow this project's [Code of Conduct](https://www.apache.org/foundation/policies/conduct)