fix: update lego.

vendor/google.golang.org/api/gensupport/buffer.go

@@ -11,7 +11,8 @@ import (
 	"google.golang.org/api/googleapi"
 )
 
-// MediaBuffer buffers data from an io.Reader to support uploading media in retryable chunks.
+// MediaBuffer buffers data from an io.Reader to support uploading media in
+// retryable chunks. It should be created with NewMediaBuffer.
 type MediaBuffer struct {
 	media io.Reader
 
@@ -22,6 +23,7 @@ type MediaBuffer struct {
 	off int64
 }
 
+// NewMediaBuffer initializes a MediaBuffer.
 func NewMediaBuffer(media io.Reader, chunkSize int) *MediaBuffer {
 	return &MediaBuffer{media: media, chunk: make([]byte, 0, chunkSize)}
 }