fix warnings

Author: sylvestre

tests/by-util/test_tee.rs

@@ -170,7 +170,6 @@ mod linux_only {
     use std::time::Duration;
     use uutests::at_and_ucmd;
     use uutests::new_ucmd;
-    use uutests::util::TestScenario;
     use uutests::util_name;
 
     fn make_broken_pipe() -> File {

tests/by-util/test_test.rs

@@ -5,7 +5,6 @@
 
 // spell-checker:ignore (words) egid euid pseudofloat
 
-use std::thread::sleep;
 use uutests::at_and_ucmd;
 use uutests::new_ucmd;
 use uutests::util::TestScenario;