Better changelog entry

CHANGELOG.md

@@ -5,7 +5,7 @@ This is a changelog for Piwik platform developers. All changes for our HTTP API'
 ## Piwik 2.15.0
 
 ### Breaking Changes
-* We marked the method `Dimension::getId()` as final.
+* The method `Dimension::getId()` has been set as `final`. It is not allowed to overwrite this method.
 
 ## Piwik 2.14.0
 
@@ -334,4 +334,4 @@ We are using `@since` annotations in case we are introducing new API's to make i
  -->
 
 Find the general Piwik Changelogs for each release at [piwik.org/changelog](http://piwik.org/changelog/)
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