DOC Document new redirector 404 in changelog

en/04_Changelogs/5.2.0.md

@@ -196,6 +196,7 @@ This will now fail by throwing an exception, which means your form won't render
 
 - A new [`SiteTree.hide_pagetypes`](api:SilverStripe\CMS\Model\SiteTree->hide_pagetypes) configuration property has been added. Unlike [`SiteTree.hide_ancestor`](api:SilverStripe\CMS\Model\SiteTree->hide_ancestor) (which has [now been deprecated](#api-silverstripe-cms)), this is an array. This allows you to define all page types that should be hidden in a single configuration property in your YAML configuration.
 - You can now upload [Braille ASCII file format](https://en.wikipedia.org/wiki/Braille_ASCII) (`.brf`) files to the CMS without needing to modify the [allowed file types](/developer_guides/files/allowed_file_types/).
+- Redirector pages with link to a missing or unpublished page/file will now return a 404 response. You can revert to the previous behaviour by setting the [`RedirectorPageController.missing_redirect_is_404`](api:SilverStripe\CMS\Model\RedirectorPageController->missing_redirect_is_404) configuration property to `false`.
 
 ## API changes