docs: document typing suppression

Signed-off-by: Ingo Müller <[email protected]>

test/python/dialects/substrait/e2e_duckdb.py

@@ -49,6 +49,7 @@ def testNamedTable():
   pb_plan = ss.to_binpb(plan.operation).encode()
 
   # Execute in duckdb and print result.
+  # Ignore type because DuckDB's `from_substrait` has wrong type annotation.
   query_result = con.from_substrait(proto=pb_plan)  # type: ignore
 
   print(query_result.to_arrow_table())