Update CHANGELOG for version 1.34.1 (#47681)

* Update CHANGELOG for version 1.34.0b1

Added unreleased changes for version 1.34.0b1, including a fix for BatchEndpoint defaults serialization regression.

* Update CHANGELOG for version 1.34.1

Updated version number to 1.34.1 and fixed serialization issue with BatchEndpoint defaults.

Author: lavakumarrepala

sdk/ml/azure-ai-ml/CHANGELOG.md

@@ -8,13 +8,18 @@
 
 ### Other Changes
 
+## 1.34.1 (unreleased)
+
+### Bugs Fixed
+- Fixed `BatchEndpoint` defaults serialization regression where `deployment_name` was sent to the service as snake_case instead of camelCase (`deploymentName`), causing `begin_create_or_update` to fail with "Could not find member 'deployment_name' on object of type 'BatchEndpointDefaults'". `BatchEndpoint.defaults` is now consistently exposed as a snake_case dict to users and converted to the correct wire format on serialization.
+
 ## 1.34.0 (2026-06-11)
 
 ### Features Added
 
 ### Bugs Fixed
 
-- Fixed `BatchEndpoint` defaults serialization regression where `deployment_name` was sent to the service as snake_case instead of camelCase (`deploymentName`), causing `begin_create_or_update` to fail with "Could not find member 'deployment_name' on object of type 'BatchEndpointDefaults'". `BatchEndpoint.defaults` is now consistently exposed as a snake_case dict to users and converted to the correct wire format on serialization.
+
 - Fixed cross-tenant registry endpoint resolution for deployment template operations by using the registry discovery API instead of ARM calls.
 - Fixed deployment template update failing with immutable field errors by ensuring `allowedInstanceType` and `allowedEnvironmentVariableOverrides` are properly round-tripped during serialization.