Update docs/introduction/read_and_write.rst

Co-authored-by: Will Jones <willjones127@gmail.com>

Author: eddyxu

docs/introduction/read_and_write.rst

@@ -78,8 +78,8 @@ or :py:meth:`~lance.write_dataset` with ``mode=append``.
   2  Carla   37
 
   >>> new_table2 = pa.Table.from_pylist([{"name": "David", "age": 42}])
-  >>> ds2 = lance.write_dataset(new_table2, "./insert_example.lance", mode="append")
-  >>> ds2.to_table().to_pandas()
+  >>> ds = lance.write_dataset(new_table_2, ds, mode="append")
+  >>> ds.to_table().to_pandas()
       name  age
   0  Alice   20
   1    Bob   30