changelog: add notes about closing #12636 #9827

[skip ci]

CHANGELOG.md

@@ -28,6 +28,7 @@
 
 * **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)
+* **Postgres/MySQL/MSSQL**: Fix connection leak [#12636](https://github.com/grafana/grafana/issues/12636) [#9827](https://github.com/grafana/grafana/issues/9827)
 
 # 5.2.1 (2018-06-29)