remove dead code

common/block.go

@@ -385,12 +385,3 @@ func (pb *posBuf) Read(p []byte) (int, error) {
 	pb.Pos += pl
 	return pl, nil
 }
-
-func (pb *posBuf) ReadByte() (byte, error) {
-	if pb.Pos >= len(pb.Data) {
-		return 0, io.EOF
-	}
-	c := pb.Data[pb.Pos]
-	pb.Pos++
-	return c, nil
-}