update changelog

Author: Deary Hudson

CHANGELOG.md

@@ -22,6 +22,7 @@
 1. [15549](https://github.com/influxdata/influxdb/pull/15549): UI/Task edit functionality fixed
 1. [15559](https://github.com/influxdata/influxdb/pull/15559): Exiting a configuration of a dashboard cell now properly renders the cell content
 1. [15556](https://github.com/influxdata/influxdb/pull/15556): Creating a check now displays on the checklist
+1. [15647](https://github.com/influxdata/influxdb/pull/15647): Ensures labels are unique by organization in the kv store
 
 ## v2.0.0-alpha.18 [2019-09-26]