Add Changelog entry for new permissions for build artifacts

[ci skip]

CHANGELOG

@@ -54,6 +54,7 @@ v 8.4.0 (unreleased)
   - Allow broadcast messages to be edited
   - Autosize Markdown textareas
   - Import GitHub wiki into GitLab
+  - Add reporters ability to download and browse build artifacts (Andrew Johnson)
 v 8.3.4
   - Use gitlab-workhorse 0.5.4 (fixes API routing bug)