修正挑战模式下, 排行榜无法正确获取的bug

doc/api.md

@@ -325,4 +325,5 @@
             "next": 1621008900000							// 下一个活动开始时间, 没有该字段或undefined的话, 说明没有即将开始的活动
         }
     }
-```
+```
+

src/services/GameLogic.ts

@@ -166,7 +166,7 @@ export async function updateExamRank({shop, level, accountId, score, session, mo
   score: number,
   mode: number,
   session: string}) {
-    const totalKey = rankKey(shop, 'exam', mode)
+    const totalKey = rankKey(shop, level, mode)
     await updateRank(accountId, score, totalKey)
   }