adding changes to CHANGELOG

Author: Azfaar Qureshi

opentelemetry-sdk/CHANGELOG.md

@@ -9,6 +9,7 @@
 - Update exception handling optional parameters, add escaped attribute to record_exception
   ([#1365](https://github.com/open-telemetry/opentelemetry-python/pull/1365))
 - Rename Record in Metrics SDK to Accumulation ([#1373](https://github.com/open-telemetry/opentelemetry-python/pull/1373))
+- Rename Meter class to Accumulator in Metrics SDK ([#1372](https://github.com/open-telemetry/opentelemetry-python/pull/1372))
 
 ## Version 0.15b0