remove exclamation mark from string-program

string-program/src/main.rs

@@ -1,5 +1,5 @@
 fn main() {
-    let s = String::from("hello!");
+    let s = String::from("hello");
     println!("{}", s);
     println!("size of string on stack: {}", std::mem::size_of_val(&s));
 }