Mention validation status change in changelog

see #3808 (comment)

Author: soyuka

CHANGELOG.md

@@ -73,7 +73,7 @@
 * Tests: adds a method to retrieve the CookieJar in the test Client `getCookieJar`
 * Tests: Fix the registration of the `test.api_platform.client` service when the `FrameworkBundle` bundle is registered after the `ApiPlatformBundle` bundle (#3928)
 * Validator: Add the violation code to the violation properties (#3857)
-* Validator: Allow customizing the validation error status code (#3808)
+* Validator: Allow customizing the validation error status code. **BC** Status code for validation errors is now 422, use `exception_to_status` to fallback to 400 if needed (#3808). 
 * Validator: Autoconfiguration of validation groups generator via `ApiPlatform\Core\Validator\ValidationGroupsGeneratorInterface`
 * Validator: Deprecate using a validation groups generator service not implementing `ApiPlatform\Core\Bridge\Symfony\Validator\ValidationGroupsGeneratorInterface` (#3346)
 * Validator: Property validation through OpenAPI (#33329)