fix Rust 1.59 clippy lints

tests/by-util/test_ls.rs

@@ -1644,11 +1644,7 @@ fn test_ls_indicator_style() {
     // Same test as above, but with the alternate flags.
     let options = vec!["--classify", "--file-type", "-p"];
     for opt in options {
-        scene
-            .ucmd()
-            .arg(opt.to_string())
-            .succeeds()
-            .stdout_contains(&"/");
+        scene.ucmd().arg(opt).succeeds().stdout_contains(&"/");
     }
 
     // Classify and File-Type all contain indicators for pipes and links.

tests/by-util/test_relpath.rs

@@ -64,7 +64,7 @@ const TESTS: [TestCase; 10] = [
 #[allow(clippy::needless_lifetimes)]
 fn convert_path<'a>(path: &'a str) -> Cow<'a, str> {
     #[cfg(windows)]
-    return path.replace("/", "\\").into();
+    return path.replace('/', "\\").into();
     #[cfg(not(windows))]
     return path.into();
 }