Update CHANGELOG.md

[TimothyMothra]

Closing Issue #2251.
Updating Changelog

Checklist

• I ran Unit Tests locally.
• CHANGELOG.md updated with one line description of the fix, and a link to the original issue if available.

For significant contributions please make sure you have completed the following items:

• Design discussion issue #
• Changes in public surface reviewed

The PR will trigger build, unit tests, and functional tests automatically. Please follow these instructions to build and test locally.

Notes for authors:

• FxCop and other analyzers will fail the build. To see these errors yourself, compile localy using the Release configuration.

Notes for reviewers:

• We support comment build triggers
  • /AzurePipelines run will queue all builds
  • /AzurePipelines run <pipeline-name> will queue a specific build