fix(backtracking): minor mistake in Rust code for subset_sum_ii (#1487)

* fix(backtracking): minor mistake in Rust code for subset_sum_ii

* Update subset_sum_ii.rs

---------

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

codes/rust/chapter_backtracking/subset_sum_ii.rs

@@ -33,7 +33,7 @@ fn backtrack(
         // 尝试：做出选择，更新 target, start
         state.push(choices[i]);
         // 进行下一轮选择
-        backtrack(state, target - choices[i], choices, i, res);
+        backtrack(state, target - choices[i], choices, i + 1, res);
         // 回退：撤销选择，恢复到之前的状态
         state.pop();
     }

zh-hant/codes/rust/chapter_backtracking/subset_sum_ii.rs

@@ -33,7 +33,7 @@ fn backtrack(
         // 嘗試：做出選擇，更新 target, start
         state.push(choices[i]);
         // 進行下一輪選擇
-        backtrack(state.clone(), target - choices[i], choices, i, res);
+        backtrack(state.clone(), target - choices[i], choices, i + 1, res);
         // 回退：撤銷選擇，恢復到之前的狀態
         state.pop();
     }