Update and Pin DuckDB version

[keckelt]

We started off with v0.3.4, but v0.6.1 is already available: https://github.com/duckdb/duckdb/releases

Due to some breaking changes, the database must be exported from the old version and re-imported with new version, creating a new .duckdb file. See https://duckdb.org/docs/sql/statements/export

This leads to the current setup not working. Therefore the accepted version of range of duckdb should also be changed in order to avoid upgrades to unsupported versions.