Added CHANGELOG entry

Author: rads-1996

sdk/monitor/azure-monitor-opentelemetry-exporter/CHANGELOG.md

@@ -8,6 +8,8 @@
   ([#41733](https://github.com/Azure/azure-sdk-for-python/pull/41733))
 - Added customer-facing statsbeat preview.
   ([#41669](https://github.com/Azure/azure-sdk-for-python/pull/41669))
+- Added RateLimited Sampler 
+  ([#41925](https://github.com/Azure/azure-sdk-for-python/pull/41925))
 
 ### Breaking Changes