Refactor comments.

Author: Luca Palmieri

jira-wip/src/koans/02_ticket_store/07_vec.rs

@@ -41,9 +41,10 @@ mod vec {
 
         /// List will return a `Vec`.
         /// Check the Rust book for a primer: https://doc.rust-lang.org/book/ch08-01-vectors.html
-        /// The Rust documentation for HashMap will also be handy: https://doc.rust-lang.org/std/collections/struct.HashMap.html
+        /// The Rust documentation for `HashMap` will also be handy:
+        /// https://doc.rust-lang.org/std/collections/struct.HashMap.html
         pub fn list(&self) -> Vec<&Ticket> {
-            __
+           todo!()
         }
 
         fn generate_id(&mut self) -> TicketId {