Move changelog entry to unreleased section

CHANGELOG.md

@@ -13,6 +13,10 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 This update is a breaking change of the unstable Metrics API.
 Code instrumented with the `go.opentelemetry.io/otel/metric` will need to be modified.
 
+### Added
+
+- Add go 1.18 to our compatibility tests. (#2679)
+
 ### Changed
 
 - The metrics API has been significantly changed. (#2587)
@@ -46,7 +50,6 @@ Code instrumented with the `go.opentelemetry.io/otel/metric` will need to be mod
   Zero or negative values will not be changed to the default value like `WithSpanLimits` does.
   Setting a limit to zero will effectively disable the related resource it limits and setting to a negative value will mean that resource is unlimited.
   Consequentially, limits should be constructed using `NewSpanLimits` and updated accordingly. (#2637)
-- Add go 1.18 to our compatibility tests. (#2679)
 
 ### Changed