Add changelog entry

CHANGELOG.md

@@ -9,6 +9,10 @@
 - Fixed type of `SharedRenderCellElementProps.schema` to be optional ([#5704](https://github.com/elastic/eui/pull/5704))
 - Fixed generated type definition file referencing nonexistant Jest util ([#5704](https://github.com/elastic/eui/pull/5704))
 
+**Breaking changes**
+
+- `EuiDataGrid` now forces `isExpandable` to be true if any `cellActions` are passed, as keyboard users are otherwise unable to access cell actions without the expansion popover ([#5710](https://github.com/elastic/eui/pull/5710))
+
 ## [`51.0.0`](https://github.com/elastic/eui/tree/v51.0.0)
 
 - Enhanced `EuiSuggest` to fire the `onItemClick` callback on Enter key press as well as clicks ([#5693](https://github.com/elastic/eui/pull/5693))