Preparing CHANGELOG.md

com.unity.perception/CHANGELOG.md

 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
-## [Unreleased]
-
-### Added
-
-### Changed
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-### Deprecated
-
-### Removed
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-### Fixed
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-## [0.4.0-preview.1] - 2020-08-07
+## [0.4.0-preview.1] - 2020-09-03
 
 ### Added