Move struct update syntax to speaker notes (#2597)

src/user-defined-types/named-structs.md

@@ -27,9 +27,6 @@ fn main() {
     let age = 39;
     let avery = Person { name, age };
     describe(&avery);
-
-    let jackie = Person { name: String::from("Jackie"), ..avery };
-    describe(&jackie);
 }
 ```
 
@@ -49,8 +46,20 @@ Key Points:
     not important.
 - If you already have variables with the right names, then you can create the
   struct using a shorthand.
-- The syntax `..avery` allows us to copy the majority of the fields from the old
-  struct without having to explicitly type it all out. It must always be the
-  last element.
+
+## More to Explore
+
+- You can also demonstrate the struct update syntax here:
+
+  ```rust,ignore
+  let jackie = Person { name: String::from("Jackie"), ..avery };
+  ```
+
+- It allows us to copy the majority of the fields from the old struct without
+  having to explicitly type it all out. It must always be the last element.
+
+- It is mainly used in combination with the `Default` trait. We will talk about
+  struct update syntax in more detail on the slide on the `Default` trait, so we
+  don't need to talk about it here unless students ask about it.
 
 </details>