updated release notes

com.unity.render-pipelines.lightweight/CHANGELOG.md

 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
-- Fixed Property (_WorldToShadow) exceeds previous array size (5 vs 1) warning
+- When you change a Shadow Cascade option in the Pipeline Asset, this no longer warns you that you've exceeded the array size for the _WorldToShadow property.
 
 ## [3.1.0-preview]