core: fix User.serialize (#986)

packages/hydrooj/src/model/user.ts

@@ -159,7 +159,7 @@ export class User {
         return user;
     }
 
-    serialize(_, h) {
+    serialize(h) {
         if (!this._isPrivate) {
             const fields = ['_id', 'uname', 'mail', 'perm', 'role', 'priv', 'regat', 'loginat', 'tfa', 'authn'];
             if (h?.user?.hasPerm(PERM.PERM_VIEW_DISPLAYNAME)) fields.push('displayName');