update: Bumped Event Processor and Datafile Manager versions to 0.8.1 (#673)

## Summary
Bumped Event Processor and Datafile Manager versions to `0.8.1`.

## Test plan
- Manually tested
- All existing tests pass

Author: zashraf1985

packages/optimizely-sdk/CHANGELOG.MD

@@ -6,6 +6,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+- Bumped `datafile-manager` and `event-processor` packages to version `0.8.1`.
 
 ## [4.5.1] - March 2, 2021