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_backtracking/permutations_i.rs

@@ -37,7 +37,7 @@ fn permutations_i(nums: &mut [i32]) -> Vec<Vec<i32>> {
 
 /* Driver Code */
 pub fn main() {
-    let mut nums = [ 1, 2, 3 ];
+    let mut nums = [1, 2, 3];
 
     let res = permutations_i(&mut nums);