docs(): updated changelog

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Enhancements
 * **Alerting**: Added Telegram alert notifier [#7098](https://github.com/grafana/grafana/pull/7098), thx [@leonoff](https://github.com/leonoff)
 * **Templating**: Make $__interval and $__interval_ms global built in variables that can be used in by any datasource (in panel queries), closes [#7190](https://github.com/grafana/grafana/issues/7190), closes [#6582](https://github.com/grafana/grafana/issues/6582)
+* **S3 Image Store**: External s3 image store (used in alert notifications) now support AWS IAM Roles, closes [#6985](https://github.com/grafana/grafana/issues/6985), [#7058](https://github.com/grafana/grafana/issues/7058) thx [@mtanda](https://github.com/mtanda)
 
 # 4.1.0 (2017-01-11)