fix(enums3): add extra tuple comment

Author: shadows-withal

exercises/enums/enums3.rs

@@ -52,7 +52,7 @@ mod tests {
             position: Point { x: 0, y: 0 },
             color: (0, 0, 0),
         };
-        state.process(Message::ChangeColor((255, 0, 255)));
+        state.process(Message::ChangeColor((255, 0, 255))); // Remember: The extra parentheses mark a tuple type.
         state.process(Message::Echo(String::from("hello world")));
         state.process(Message::Move(Point { x: 10, y: 15 }));
         state.process(Message::Quit);