Revert "Update notes"

This reverts commit 4dbd847a.

release-21d.md was erroneously modified.  It should have been
done to release-21e.md, a new file.  We've already released 21d.
2 jobs for master in 18 minutes and 16 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #1640
linux
linux-runner

00:18:16

passed #1641
osx
osx-runner

00:09:48