x509roots/fallback: update bundle

This is an automated CL which updates the NSS root bundle.

[git-generate]
go generate ./x509roots

Change-Id: I9bad7b49959a336a125bdc3aa340c94292b26899
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/766500
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Gopher Robot <gobot@golang.org>
Reviewed-by: Roland Shoemaker <roland@golang.org>

Author: gopherbot