Update CHANGELOG.md and versions

Author: rsareddy0329

CHANGELOG.md

@@ -1,5 +1,16 @@
 # Changelog
 
+## v3.1.1 (2025-12-10)
+
+### Bug fixes and Other Changes
+* Add validation to bedrock reward models
+* Hyperparameter issue fixes, Add validation s3 output path
+* Fix the recipe selection for multiple recipe scenario
+* Train wait() timeout exception handling
+* Update example notebooks to reflect recent code changes
+* Update `model_package_group_name`  param to `model_package_group`  in finetuning interfaces
+* remove `dataset` param for benchmark evaluator
+
 ## v3.1.0 (2025-12-03)
 
 ### Features