add changelog entry

Author: datwelk

CHANGELOG.md

@@ -35,6 +35,8 @@
       - FIXED: Bicycle and foot profiles now don't route on proposed ways [#6615](https://github.com/Project-OSRM/osrm-backend/pull/6615)
     - Routing:
       - FIXED: Fix adding traffic signal penalties during compression [#6419](https://github.com/Project-OSRM/osrm-backend/pull/6419)
+    - Debug tiles:
+      - FIXED: Ensure speed layer features have unique ids. [#6726](https://github.com/Project-OSRM/osrm-backend/pull/6726)
 # 5.27.1
   - Changes from 5.27.0
     - Misc: