docs(changelog): adding behavioral change info #2531

Author: ChronosSF

CHANGELOG.md

@@ -13,6 +13,9 @@ All notable changes for each version of this project will be documented in this
     - `IgxRowComponent` -> `IgxRowDirective`
     - `IgxHierarchicalGridBaseComponent` -> `IgxHierarchicalGridBaseDirective`
 
+- `IgxGrid`, `IgxTreeGrid`, `IgxHierarchicalGrid`
+    - **Behavioral Change** - Pinning columns is no longer automatically prevented when the pinning area would exceed the size of the grid.
+
 ## 8.2.4
 
 ### RTL Support