chgrp: unstripped error on operation not permitted error

uutils coreutils
```
$ cargo run -p uu_chgrp 10000 a
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.12s
     Running `target/debug/chgrp 10000 a`
chgrp: changing group of 'a': Operation not permitted (os error 1)
```
gnu coreutils
```
$ chgrp 10000 a
chgrp: changing group of 'a': Operation not permitted
```