make title consistent

Author: eddyxu

docs/introduction/read_and_write.rst

@@ -50,8 +50,8 @@ You will need to provide a :py:class:`pyarrow.Schema` for the dataset in this ca
 :py:meth:`lance.write_dataset` supports writing :py:class:`pyarrow.Table`, :py:class:`pandas.DataFrame`,
 :py:class:`pyarrow.dataset.Dataset`, and ``Iterator[pyarrow.RecordBatch]``.
 
-Adding data to an existing dataset
-----------------------------------
+Adding Rows
+-----------
 
 To insert data into your dataset, you can use either :py:meth:`LanceDataset.insert <lance.LanceDataset.insert>`
 or :py:meth:`~lance.write_dataset` with ``mode=append``.
@@ -161,7 +161,7 @@ more efficient to use the merge insert operation described below.
     dataset.update({"age": new_age}, where=f"name='{name}'")
 
 Merge Insert
-~~~~~~~~~~~~
+------------
 
 Lance supports a merge insert operation.  This can be used to add new data in bulk
 while also (potentially) matching against existing data.  This operation can be used