Update doc/python/v6-changes.md

Author: LiamConnors

doc/python/v6-changes.md

@@ -59,7 +59,7 @@ Plotly.py now takes advantage of recent changes in how Plotly.js handles typed a
 
 ## Dataframe Support
 
-Plotly Express now uses [Narwhals](https://narwhals-dev.github.io/narwhals/) to natively support pandas, Polars, and PyArrow.
+Plotly Express now uses [Narwhals](https://narwhals-dev.github.io/narwhals/) to natively support pandas, Polars, and PyArrow. With this change, the [performance](https://plotly.com/python/performance/) of using Polars or PyArrow with Plotly Express is significantly improved. 
 
 ## Mapbox Deprecation