api: promote next to go1.27

Change-Id: Ie368ea1442ad3e891dd7a870677f8ec920664db1
Reviewed-on: https://go-review.googlesource.com/c/go/+/784680
Auto-Submit: Gopher Robot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>