[EventHubs] prepare for 5.11.1 patch release (Azure#26312)

- update release date in CHANGELOG

Author: jeremymeng

sdk/eventhub/event-hubs/CHANGELOG.md

@@ -1,17 +1,11 @@
 # Release History
 
-## 5.11.1 (Unreleased)
-
-### Features Added
-
-### Breaking Changes
+## 5.11.1 (2023-06-23)
 
 ### Bugs Fixed
 
 - Fix a regression of missing `getToken` calls when renewing tokens.
 
-### Other Changes
-
 ## 5.11.0 (2023-06-08)
 
 ### Features Added