Remove "I AM NOT DONE" and the verify mode and add AppState

exercises/16_lifetimes/lifetimes1.rs

@@ -8,8 +8,6 @@
 // Execute `rustlings hint lifetimes1` or use the `hint` watch subcommand for a
 // hint.
 
-// I AM NOT DONE
-
 fn longest(x: &str, y: &str) -> &str {
     if x.len() > y.len() {
         x

exercises/16_lifetimes/lifetimes2.rs

@@ -6,8 +6,6 @@
 // Execute `rustlings hint lifetimes2` or use the `hint` watch subcommand for a
 // hint.
 
-// I AM NOT DONE
-
 fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
     if x.len() > y.len() {
         x

exercises/16_lifetimes/lifetimes3.rs

@@ -5,8 +5,6 @@
 // Execute `rustlings hint lifetimes3` or use the `hint` watch subcommand for a
 // hint.
 
-// I AM NOT DONE
-
 struct Book {
     author: &str,
     title: &str,