updated changelog for the 6.6.0 release (#4518)

Signed-off-by: Sean Porter <portertech@gmail.com>

CHANGELOG.md

@@ -8,18 +8,20 @@ Versioning](http://semver.org/spec/v2.0.0.html).
 
 ## Unreleased
 
+## [6.6.0] - 2021-11-25
+
 ### Added
 - Add backend label to logged metrics.
 
 ### Fixed
-- In addition to the context error print the connection error when sensu-go can't connect to etcd.
+- In addition to the context error print the connection error when
+sensu-go can't connect to etcd.
+- Fixed a bug where sensu-backend could crash if the BackendIDGetter
+encounters etcd client unavailability.
 
 ### Changed
-- Empty and zero value configuration parameters for `etcd` do not overwrite
-  defaults anymore.
-### Fixed
-- Fixed a bug where sensu-backend could crash if the BackendIDGetter encounters
-etcd client unavailability.
+- Empty and zero value configuration parameters for `etcd` do not
+overwrite defaults anymore.
 
 ## [6.5.5] - 2021-11-19