[duckdb-labs bot] Bump DuckDB submodule (#380)

Bump duckdb submodule:
- Target branch: v1.5-variegata
- Date: 2026-03-16 06:14:13
- DuckDB SHA: 3ada6fd54bcf11dc9a02e24f5954b9560a3dc088
- Trigger:
https://github.com/duckdb/duckdb-python/actions/runs/23129895059

Author: evertlammerts