clarify code example ch6.3

Author: adrientremblay

listings/ch06-enums-and-pattern-matching/no-listing-12-if-let/src/main.rs

@@ -1,6 +1,6 @@
 fn main() {
-    let some_u8_value = Some(0u8);
     // ANCHOR: here
+    let some_u8_value = Some(0u8);
     if let Some(3) = some_u8_value {
         println!("three");
     }