Update release schedule, notes

Bug: skia:
Change-Id: I993eec22654edf93ea93e37282b0e08d19acd589
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/281516
Reviewed-by: Joe Gregorio <jcgregorio@google.com>
Reviewed-by: Heather Miller <hcm@google.com>
Commit-Queue: Heather Miller <hcm@google.com>
3 files changed