Prepare changelog for release. (Azure#50437)

Author: nick863

sdk/ai/Azure.AI.Agents.Persistent/CHANGELOG.md

@@ -1,16 +1,10 @@
 # Release History
 
-## 1.1.0-beta.2 (Unreleased)
-
-### Features Added
-
-### Breaking Changes
+## 1.1.0-beta.2 (2025-06-04)
 
 ### Bugs Fixed
 - Fixed uploading files with non ASCII symbols in names.
 
-### Other Changes
-
 ## 1.1.0-beta.1 (2025-05-21)
 
 ### Features Added