fix(move_semantics2): add expected output comment

You can easily get this to compile with `vec0` being `[]` and `vec1` being `[22, 44, 66, 88]`

exercises/move_semantics/move_semantics2.rs

@@ -2,6 +2,10 @@
 // Make me compile without changing line 13 or moving line 10!
 // Execute `rustlings hint move_semantics2` or use the `hint` watch subcommand for a hint.
 
+// Expected output:
+// vec0 has length 3 content `[22, 44, 66]`
+// vec1 has length 4 content `[22, 44, 66, 88]`
+
 // I AM NOT DONE
 
 fn main() {