Merge pull request #2027 from yerke/patch-2

Fix formatting in strings4.rs

exercises/09_strings/strings4.rs

@@ -4,6 +4,7 @@ fn placeholder() {}
 fn string_slice(arg: &str) {
     println!("{arg}");
 }
+
 fn string(arg: String) {
     println!("{arg}");
 }