fix changelog repeat sections

Author: AdinAck

CHANGELOG.md

@@ -6,8 +6,6 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
-### Added
-
 ### Changed
 - Updated the `cast` dependency from 0.2 to 0.3
 - Fixed typo in setup of complementary channels
@@ -23,6 +21,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 - Wrong mode when using PWM channel 2 of a two-channel timer
 - `adc_values` example conversion error
+- Fixed typo in setup of complementary channels
 
 ## [v0.18.0] - 2021-11-14