Added changelog for project namespace performance

CHANGELOG

@@ -4,6 +4,7 @@ v 8.1.0 (unreleased)
   - Add support for creating directories from Files page (Stan Hu)
   - Allow removing of project without confirmation when JavaScript is disabled (Stan Hu)
   - Support filtering by "Any" milestone or issue and fix "No Milestone" and "No Label" filters (Stan Hu)
+  - Improved performance of finding projects by their namespace
   - Fix bug where transferring a project would result in stale commit links (Stan Hu)
   - Include full path of source and target branch names in New Merge Request page (Stan Hu)
   - Add user preference to view activities as default dashboard (Stan Hu)