proto: remove commented-out code (#704)
proto: remove commented-out code (#704)

The "return 0, errOverflow" already tells that x is always zero.
If there is a mistake, this code path should be fixed,
otherwise code that is disabled does not add any value.
fuchsia-mirror/third_party-github.com-golang-protobuf,golang/protobuf,golang/protobuf,fuchsia-mirror/third_party-github.com-golang-protobuf