This is a no-op change in preparation of removing support for weak fields.
It allows users to keep enabling ProtoLegacy in general,
but also disable weak field support independently.
For golang/protobuf#1666
Change-Id: Ic3cb90d937e21a817ddbbb36029274be8b5f2513
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/641635
Reviewed-by: Chressie Himpel <chressie@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>