chroot: fix unused import on Android

[miles170]

See https:/uutils/coreutils/actions/runs/4486101640/jobs/7888344087

warning: unused import: `is_ci`
 --> tests/by-util/test_chroot.rs:3:27
  |
3 | use crate::common::util::{is_ci, run_ucmd_as_root, TestScenario};
  |                           ^^^^^
  |
  = note: `#[warn(unused_imports)]` on by default

warning: `coreutils` (test "tests") generated 1 warning
    Finished test [unoptimized + debuginfo] target(s) in 5m 12s
     Running unittests src/bin/coreutils.rs (target/debug/deps/coreutils-c1c95fca0b7a1e35)

[github-actions]

GNU testsuite comparison:

Congrats! The gnu test tests/tail-2/inotify-dir-recreate is no longer failing!

[cakebaker]

Thanks!