docs: update links to duckdb csv parameters

[amoeba]

Please describe the issue

There are two locations in docstrings where Ibis links to https://duckdb.org/docs/data/csv#parameters.

• ibis/expr/api.py
• ibis/backends/duckdb/__init__.py

If you visit this URL in a browser, you get redirected to https://duckdb.org/docs/data/csv/overview.html but are missing the #parameters fragment so you aren't scrolled to the intended section of the page, https://duckdb.org/docs/data/csv/overview.html#parameters. This is because DuckDB changed this URL at some point and, when they set up the redirect, they didn't set it up in such a way as to preserve fragments.

I'll put up a PR in a sec to change the URLs.

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