docs(blog): mention dask in the pandeprecation post (#9899)

Mention dask in the deprecation post.

docs/posts/farewell-pandas/index.qmd

@@ -8,13 +8,18 @@ categories:
     - community
 ---
 
-**TL; DR**: we are deprecating the `pandas` backend and will be removing it in version 10.0.
+**TL; DR**: we are deprecating the `pandas` and `dask` backends and will be
+removing them in version 10.0.
 
 There is no feature gap between the `pandas` backend and our default DuckDB
 backend, and DuckDB is _much_ more performant.  `pandas` DataFrames will still
 be available as _format_ for getting data from Ibis, we just won't support using
 `pandas` to execute queries.
 
+Most of the rationale below applies to the Dask backend since it has so much in
+common with Pandas. Dask is a great project and people should continue to use
+it outside the Ibis context.
+
 ## Why `pandas`? And a bit of Ibis history
 
 Way back in the early days of Ibis, there was only one backend: Impala.  Not