core: 支持显示时空限制 (#65)

虽然有点丑，但是能用

packages/migrate-vijos/package.json

@@ -1,6 +1,6 @@
 {
     "name": "@hydrooj/migrate-vijos",
-    "version": "1.4.0",
+    "version": "1.4.1",
     "main": "package.json",
     "repository": "git@github.com:hydro-dev/Hydro.git",
     "author": "undefined <i@undefined.moe>",

packages/migrate-vijos/script.ts

@@ -74,7 +74,6 @@ const tasks = {
                 return res;
             },
         },
-        ac_msg: 'acMsg',
         parent_doc_id: {
             field: 'parentId',
             processer: (parentId, doc) => {