protobuf v36 added `--<lang>_prefix=COMMAND`, which runs a protoc plugin
through a wrapper command instead of looking it up on PATH. That lets the
Go generator be declared in go.mod like every other tool dependency, so
its version is tracked in one place instead of three.
go-generate-fast rejects protoc flags it doesn't know, so the fork pin
moves to a commit that teaches it about --go_prefix.
Part of #7099.
Igor Sirotin
b28d8c06cf