chore: clarify changelog bugfix vs breaking change

Author: heitorlessa

CHANGELOG.md

@@ -7,7 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 
 ### Fixed
-- **Metrics**: Cold start metric is now completely separate from application metrics dimensions, making it easier and cheaper to visualize
+- **Metrics**: Cold start metric is now completely separate from application metrics dimensions, making it easier and cheaper to visualize.
+    - This is a breaking change if you were graphing/alerting on both application metrics with the same name to compensate this previous malfunctioning
+    - Marked as bugfix as this is the intended behaviour since the beginning, as you shouldn't have the same application metric with different dimensions
 
 ## [1.3.1] - 2020-08-22
 ### Fixed