Update changelog

Author: ocelotl

opentelemetry-sdk/CHANGELOG.md

@@ -4,7 +4,7 @@
 
 - Make `SpanProcessor.on_start` accept parent Context
   ([#1251](https://github.com/open-telemetry/opentelemetry-python/pull/1251))
-- Add debug Controller and set initial checkpoint timestamp in aggregators
+- Set initial checkpoint timestamp in aggregators
   ([#1237](https://github.com/open-telemetry/opentelemetry-python/pull/1237))
 
 ## Version 0.14b0