all: update to use Go1.16.1
all: update to use Go1.16.1

Change-Id: I9d899131c09f16b4de7cbece8099aa463eec0f75
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/298049
Trust: Joe Tsai <ad9e03fbec35106ba742f446a098eef3d5e31d20@digital-static.net>
Reviewed-by: Damien Neil <7e091e9a80da888fcd7836fd3c6b7b85f4677c12@google.com>

protocolbuffers/protobuf-go,protocolbuffers/protobuf-go