chore: remove quiz4

exercises/quiz4.rs

@@ -1,23 +0,0 @@
-// quiz4.rs
-// This quiz covers the sections:
-// - Modules
-// - Macros
-
-// Write a macro that passes the quiz! No hints this time, you can do it!
-
-// I AM NOT DONE
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn test_my_macro_world() {
-        assert_eq!(my_macro!("world!"), "Hello world!");
-    }
-
-    #[test]
-    fn test_my_macro_goodbye() {
-        assert_eq!(my_macro!("goodbye!"), "Hello goodbye!");
-    }
-}