Modify CHANGELOG.md

Author: IcySteam

CHANGELOG.md

@@ -21,6 +21,9 @@ Increment the:
 * [SDK] Fix instrumentation scope attributes evaluated in equal method
   [#3214](https://github.com/open-telemetry/opentelemetry-cpp/pull/3214)
 
+* [SDK] Implement spec: MetricFilter
+  [#3235](https://github.com/open-telemetry/opentelemetry-cpp/pull/3235)
+
 * [EXPORTER] Fix scope attributes missing from otlp traces metrics
   [#3185](https://github.com/open-telemetry/opentelemetry-cpp/pull/3185)