docs: fix Databricks Vector Search demo notebook (#25504)
**Description:** This PR fixes an issue in the demo notebook of
Databricks Vector Search in "Work with Delta Sync Index" section.
**Issue:** N/A
**Dependencies:** N/A
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Co-authored-by: Chengzu Ou <chengzu.ou@databrick.com>
Co-authored-by: Erick Friis <erick@langchain.dev>
