Update changelog (#42252)

Author: aavasthy

sdk/cosmos/azure-cosmos/CHANGELOG.md

@@ -14,6 +14,7 @@
 
 #### Other Changes
 * Changed to include client id in headers for all requests. See [PR 42104](https://github.com/Azure/azure-sdk-for-python/pull/42104).
+* Added an option to override AAD audience scope through environment variable. See [PR 42228](https://github.com/Azure/azure-sdk-for-python/pull/42228).
 
 ### 4.14.0b1 (2025-07-14)