fix(datasets): default to DuckDB in in-memory mode

[deepyaman]

Description

https://github.com/kedro-org/kedro-plugins/pull/893#discussion_r1804632435

Development notes

TODO: Add unit test (make sure connection caching works correctly?)

Checklist

• [ ] Opened this PR as a 'Draft Pull Request' if it is work-in-progress
• [ ] Updated the documentation to reflect the code changes
• [ ] Added a description of this change in the relevant RELEASE.md file
• [ ] Added tests to cover my changes
• [ ] Received approvals from at least half of the TSC (required for adding a new, non-experimental dataset)

[deepyaman]

Thanks all for reviewing! I just updated the tests/release notes, so I'm going to go ahead and merge this once builds pass.