更新第六章实例

listings/ch06-enums-and-pattern-matching/no-listing-06-option-examples/src/main.rs

@@ -1,7 +1,7 @@
 fn main() {
     // ANCHOR: here
     let some_number = Some(5);
-    let some_string = Some("a string");
+    let some_char = Some('e');
 
     let absent_number: Option<i32> = None;
     // ANCHOR_END: here