Update CHANGELOG

CHANGELOG

@@ -50,6 +50,7 @@ v 8.9.0 (unreleased)
   - An indicator is now displayed at the top of the comment field for confidential issues.
   - RepositoryCheck::SingleRepositoryWorker public and private methods are now instrumented
   - Improve issuables APIs performance when accessing notes !4471
+  - External links now open in a new tab
 
 v 8.8.4 (unreleased)
   - Ensure branch cleanup regardless of whether the GitHub import process succeeds