updated changelog

CHANGELOG

 Please view this file on the master branch, on stable branches it's out of date.
 
-v 8.5.0 (unreleased)
+v 8.6.0 (unreleased)
+  - Improve weight filter for issues
+
+v 8.5.0
   - Fix Elasticsearch blob results linking to the wrong reference ID (Stan Hu)
   - Fix duplicate "me" in tooltip of the "thumbsup" awards Emoji (Stan Hu)
   - Cache various Repository methods to improve performance (Yorick Peterse)