add projected release date to changelog (#4466)

Signed-off-by: Justin Kolberg <amd.prophet@gmail.com>

Author: amdprophet

CHANGELOG.md

@@ -6,7 +6,7 @@ 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
+## [6.5.2] - 2021-10-28
 
 ### Added
 - Added `status` & `event_type` labels to the sensu_go_event_handler_duration