test_ls.rs: remove unsafe (#12044)

Author: oech3

tests/by-util/test_ls.rs

@@ -6214,7 +6214,7 @@ fn test_acl_padding_not_inflated() {
     let scene = TestScenario::new(util_name!());
     let at = &scene.fixtures;
 
-    let uid = unsafe { libc::getuid() };
+    let uid = uucore::process::getuid();
     let names = ["file1", "file2", "file3", "file4", "file5"];
     for name in &names {
         at.touch(name);