Add changelog entry for withRequestConfig

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: renaudhartert-db

NEXT_CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Release v0.97.0
 
 ### New Features and Improvements
+ * Add `withRequestConfig(RequestConfig)` to `CommonsHttpClient.Builder` for fine-grained timeout control ([#691](https://github.com/databricks/databricks-sdk-java/pull/691)).
 
 ### Bug Fixes