changelog: add notes about closing #12379

[skip ci]

CHANGELOG.md

@@ -20,6 +20,7 @@
 
 ### Minor
 
+* **Prometheus**: Fix graph panel bar width issue in aligned prometheus queries [#12379](https://github.com/grafana/grafana/issues/12379)
 * **Dashboard**: Dashboard links not updated when changing variables [#12506](https://github.com/grafana/grafana/issues/12506)
 
 # 5.2.1 (2018-06-29)