changelog: add notes about closing #8186

[skip ci]

CHANGELOG.md

@@ -10,6 +10,7 @@
 * **Singlestat**: Make colorization of prefix and postfix optional in singlestat [#11892](https://github.com/grafana/grafana/pull/11892), thx [@ApsOps](https://github.com/ApsOps)
 * **Table**: Make table sorting stable when null values exist [#12362](https://github.com/grafana/grafana/pull/12362), thx [@bz2](https://github.com/bz2)
 * **Prometheus**: Fix graph panel bar width issue in aligned prometheus queries [#12379](https://github.com/grafana/grafana/issues/12379)
+* **Variables**: Skip unneeded extra query request when de-selecting variable values used for repeated panels [#8186](https://github.com/grafana/grafana/issues/8186), thx [@mtanda](https://github.com/mtanda)
 
 # 5.2.1 (2018-06-29)