pin ibis-substrait

`ibis-substrait` 3.1 generates substrait plans with type signatures
included in all scalar function references. The current release of
duckdb cannot execute these plans; for now we fall back to
ibis-substrait 3.0 which doesn't include this feature.

requirements.txt

@@ -4,4 +4,4 @@ ipywidgets
 altair
 pandas < 2.1
 ibis-framework[sqlite,duckdb,clickhouse]
-ibis-substrait
+ibis-substrait < 3.1