Fixing CHANGELOG.md (#42536)

Author: jeet1995

sdk/cosmos/azure-cosmos/CHANGELOG.md

@@ -10,6 +10,13 @@
 
 #### Other Changes
 
+### 4.63.4 (2024-10-15)
+
+#### Bugs Fixed
+* Fixed an issue where a `NullPointerException` was thrown with circuit breaker enabled and partition split / merge scenarios. - See [PR 42178](https://github.com/Azure/azure-sdk-for-java/pull/42178)
+* Fixed an issue when a `Batch` operation hitting end-to-end timeout would not capture diagnostics correctly. - See [PR 42178](https://github.com/Azure/azure-sdk-for-java/pull/42178)
+* Fixed an issue where holding onto a `CosmosException` instance would hold a strong reference to a `RxDocumentClientImpl` instance preventing garbage collection of the `RxDocumentClientImpl` instance. - See [PR 42178](https://github.com/Azure/azure-sdk-for-java/pull/42178)
+
 ### 4.64.0 (2024-10-10)
 
 #### Features Added