Solve more move exercises (#5)

exercises/move_semantics/move_semantics4.rs

@@ -4,8 +4,6 @@
 // freshly created vector from fill_vec to its caller.
 // Execute `rustlings hint move_semantics4` for hints!
 
-// I AM NOT DONE
-
 fn main() {
     // let vec0 = Vec::new();
 

exercises/move_semantics/move_semantics5.rs

@@ -3,13 +3,11 @@
 // adding, changing or removing any of them.
 // Execute `rustlings hint move_semantics5` for hints :)
 
-// I AM NOT DONE
-
 fn main() {
     let mut x = 100;
     let y = &mut x;
-    let z = &mut x;
     *y += 100;
+    let z = &mut x;
     *z += 1000;
     assert_eq!(x, 1200);
 }