OpenSearch sync error on dcat.describedBy

Dataset failed to be indexed.

```
2026-06-23T15:29:27.62+0000 [APP/TASK/search-sync-28036374752-2/0] OUT {'dataset_id':
'922af0ed-6d65-44c0-aa08-1c4c87ab9118', 'status_code': 400, 'error_type':
'mapper_parsing_exception', 'error_reason': "failed to parse field [dcat.describedBy] of type
[text] in document with id '922af0ed-6d65-44c0-aa08-1c4c87ab9118'. Preview of field's value:
'{accessURL=[https://www.ssa.gov/data/HAVV.html}](https://www.ssa.gov/data/HAVV.html%7D)'",
'caused_by': {'type': 'illegal_state_exception', 'reason': "Can't get text on a START_OBJECT at
1:1376"}}

2026-06-23T15:29:27.62+0000 [APP/TASK/search-sync-28036374752-2/0] OUT {'index':
{'_index': 'datasets', '_id': '922af0ed-6d65-44c0-aa08-1c4c87ab9118', 'status': 400, 'error':
{'type': 'mapper_parsing_exception', 'reason': "failed to parse field [dcat.describedBy] of
type [text] in document with id '922af0ed-6d65-44c0-aa08-1c4c87ab9118'. Preview of field's value:
'{accessURL=[https://www.ssa.gov/data/HAVV.html}](https://www.ssa.gov/data/HAVV.html%7D)'",
'caused_by': {'type': 'illegal_state_exception', 'reason': "Can't get text on a START_OBJECT at
1:1376"}}}}
```