bytes: remove obsolete comment

Change-Id: Iec4348eb674c8c64497c82e5d7cd656736cfcebd
GitHub-Last-Rev: 462c323960be0ca1c126c051ab97f72949bdc2b6
GitHub-Pull-Request: golang/go#32225
Reviewed-on: https://go-review.googlesource.com/c/go/+/178797Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/bytes/buffer.go

@@ -21,9 +21,6 @@ type Buffer struct {
 	buf      []byte // contents are the bytes buf[off : len(buf)]
 	off      int    // read at &buf[off], write at &buf[len(buf)]
 	lastRead readOp // last read operation, so that Unread* can work correctly.
-
-	// FIXME: it would be advisable to align Buffer to cachelines to avoid false
-	// sharing.
 }
 
 // The readOp constants describe the last action performed on