Remove removed new class from release notes

Author: emmadesilva

RELEASE_NOTES.md

@@ -11,7 +11,6 @@ This serves two purposes:
 
 ### Added
 - Added a new `\Hyde\Framework\Actions\PreBuildTasks\TransferMediaAssets` build task handle media assets transfers for site builds.
-- Added a new `ExternalRoute` class to represent external routes.
 - Added a new `NavigationItem::getLink()` method contain the previous `NavigationItem::getDestination()` logic, to return the link URL.
 
 ### Changed