cp: don't show msg with cp -i -v --update=older a b if a is older than b

[cakebaker]

While reviewing #7287 I noticed that we show an 'a' -> 'b' -message with cp -i -v --update=older a b if a is older than b and thus b is not overwritten:

$ echo "a" > a
$ echo "b" > b
$ cargo run cp -i -v --update=older a b
'a' -> 'b'
$ cat b
b

With GNU cp, there is no such message:

$ echo "a" > a
$ echo "b" > b
$ cp -i -v --update=older a b
$ cat b
b