vendor: update gogo/protobuf dependency

Updates to the gogo/protobuf dependency are required to correctly
generate time types. We also remove an unused windows dependency.

Signed-off-by: Stephen J Day <stephen.day@docker.com>

vendor/github.com/gogo/protobuf/plugin/marshalto/marshalto.go

@@ -420,7 +420,7 @@ func (p *marshalto) generateField(proto3 bool, numGen NumGen, file *generator.Fi
 		p.P(`if m.`, fieldname, ` != nil {`)
 		p.In()
 	}
-	packed := field.IsPacked() || (proto3 && field.IsRepeated() && generator.IsScalar(field))
+	packed := field.IsPacked() || (proto3 && field.IsPacked3())
 	wireType := field.WireType()
 	fieldNumber := field.GetNumber()
 	if packed {