Add no_cc_authors=true

This will allow Flutter recipes to auto-update without emailing all the
authors of the CLs being rolled.

See https://chromium-review.googlesource.com/c/infra/infra/+/2256318 for
more.

Change-Id: Iaec1b31ca6a80635aff0ff1c690ed074b847a524
Reviewed-on: https://flutter-review.googlesource.com/c/recipes/+/3800
Reviewed-by: Godofredo Contreras <godofredoc@google.com>
Commit-Queue: Rob Mohr <mohrr@google.com>