cargo fmt rust code (#1131)

* cargo fmt code

* Add empty line to seperate unrelated comments

* Fix review

* Update bubble_sort.rs

* Update merge_sort.rs

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Co-authored-by: Yudong Jin <krahets@163.com>

codes/rust/chapter_stack_and_queue/stack.rs

@@ -37,4 +37,4 @@ pub fn main() {
     // 判断栈是否为空
     let is_empty = stack.is_empty();
     print!("\n栈是否为空 = {is_empty}");
-}
+}