docs: added changelog entry for pr open-telemetry#3603

Author: Dudssource

CHANGELOG.md

@@ -50,6 +50,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#3524](https://github.com/open-telemetry/opentelemetry-python/pull/3524))
 - Handle `taskName` `logrecord` attribute
   ([#3557](https://github.com/open-telemetry/opentelemetry-python/pull/3557))
+- Fix `OTLPMetricExporter` ignores `preferred_aggregation` property ([#3603](https://github.com/open-telemetry/opentelemetry-python/pull/3603))
 
 ## Version 1.21.0/0.42b0 (2023-11-01)