Move the CI version of protobuf to a more recent version.
Move the CI version of protobuf to a more recent version.

apple/swift-protobuf,thomasvl/swift-protobuf,apple/swift-protobuf,thomasvl/swift-protobuf,cburrows/swift-protobuf,thomasvl/swift-protobuf,apple/swift-protobuf,apple/swift-protobuf,cburrows/swift-protobuf,cburrows/swift-protobuf,tbkka/swift-protobuf,thomasvl/swift-protobuf,cburrows/swift-protobuf,cburrows/swift-protobuf,cburrows/swift-protobuf,tbkka/swift-protobuf,apple/swift-protobuf,apple/swift-protobuf,thomasvl/swift-protobuf,thomasvl/swift-protobuf,tbkka/swift-protobuf,apple/swift-protobuf,tbkka/swift-protobuf,tbkka/swift-protobuf,thomasvl/swift-protobuf,cburrows/swift-protobuf,tbkka/swift-protobuf,tbkka/swift-protobuf