Improve tuple destructuring (#2582)

This slide had two code samples, neither of which had a `main` and thus
neither of which would run. This removes the first (which is redundant
to one a few slides earlier), adds a `main`, and expands the second to
use a 3-tuple.

Author: djmitche

src/tuples-and-arrays/destructuring.md

@@ -4,25 +4,21 @@ minutes: 5
 
 # Patterns and Destructuring
 
-When working with tuples and other structured values it's common to want to
-extract the inner values into local variables. This can be done manually by
-directly accessing the inner values:
+Rust supports using pattern matching to destructure a larger value like a tuple
+into its constituent parts:
 
 ```rust,editable
-fn print_tuple(tuple: (i32, i32)) {
-    let left = tuple.0;
-    let right = tuple.1;
-    println!("left: {left}, right: {right}");
+fn check_order(tuple: (i32, i32, i32)) -> bool {
+    let (left, middle, right) = tuple;
+    left < middle && middle < right
 }
-```
 
-However, Rust also supports using pattern matching to destructure a larger value
-into its constituent parts:
-
-```rust,editable
-fn print_tuple(tuple: (i32, i32)) {
-    let (left, right) = tuple;
-    println!("left: {left}, right: {right}");
+fn main() {
+    let tuple = (1, 5, 3);
+    println!(
+        "{tuple:?}: {}",
+        if check_order(tuple) { "ordered" } else { "unordered" }
+    );
 }
 ```