[Exercise] solve intro

exercises/intro/intro1.rs

@@ -9,7 +9,6 @@
 // when you change one of the lines below! Try adding a `println!` line, or try changing
 // what it outputs in your terminal. Try removing a semicolon and see what happens!
 
-// I AM NOT DONE
 
 fn main() {
     println!("Hello and");

exercises/intro/intro2.rs

@@ -2,8 +2,7 @@
 // Make the code print a greeting to the world.
 // Execute `rustlings hint intro2` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
 
 fn main() {
-    println!("Hello {}!");
+    println!("Hello {}!", "world");
 }