update release notes

Change-Id: Ida17b9d3da4d3a6489f62d2959379747a671fbab
Docs-Preview: https://skia.org/?cl=428982
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/428982
Reviewed-by: Joe Gregorio <jcgregorio@google.com>
Reviewed-by: Heather Miller <hcm@google.com>
Commit-Queue: Heather Miller <hcm@google.com>
Auto-Submit: Heather Miller <hcm@google.com>
2 files changed