[ServiceBus] Update Changelog (Azure#28213)

* update

* fix

Author: kashifkhan

sdk/servicebus/azure-servicebus/CHANGELOG.md

@@ -1,13 +1,11 @@
 # Release History
 
-## 7.8.2 (Unreleased)
-
-### Features Added
-
-### Breaking Changes
+## 7.8.2 (2023-01-10)
 
 ### Bugs Fixed
 
+- Fixed a bug that would cause an exception when `None` was sent to `set_state` instead of clearing session state (Issue #27582).
+
 ### Other Changes
 
 - Updated uAMQP dependency to 1.6.3.