Updating changelog for Pin major version of external dependencies (Azure#40673)

Author: jayesh-tanna

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

@@ -3,15 +3,17 @@
 ## 1.27.0 (unreleased)
 
 ### Bugs Fixed
-
 - Fix for compute Instance, disableLocalAuth property should be depend on ssh public access enabled.
 - Removing Git-related properties from job properties if a PAT token is detected in the repository URL.
 - Fix deployment creation for registry models
 
 ### Other Changes
-
 - Hub and Project are officially GA'd and no longer experimental.
-- Restrict major version auto updates for external dependencies to ensure stability and prevent build failures for breaking changes.
+
+## 1.26.4 (2025-04-23)
+
+### Other Changes
+  - Restrict major version auto updates for external dependencies to ensure stability and prevent build failures for breaking changes.
 
 ## 1.26.3 (2025-04-17)