Update release notes files

Docs-Preview: https://skia.org/?cl=258417
Bug: skia:
Change-Id: I4716231ad260f2f7f29776f7cc455c6837ec6a43
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/258417
Reviewed-by: Heather Miller <hcm@google.com>
Commit-Queue: Heather Miller <hcm@google.com>
Auto-Submit: Heather Miller <hcm@google.com>
2 files changed