changelog: update

[skip ci]

CHANGELOG.md

@@ -23,7 +23,7 @@
 * **Units**: Polish złoty currency [#12691](https://github.com/grafana/grafana/pull/12691), thx [@mwegrzynek](https://github.com/mwegrzynek)
 * **Cloudwatch**: Improved error handling [#12489](https://github.com/grafana/grafana/issues/12489), thx [@mtanda](https://github.com/mtanda)
 
-# 5.2.2 (unreleased)
+# 5.2.2 (2018-07-25)
 
 ### Minor