🐛 修复 `DailyLimiter` 的属性类型注解不适用于 py3.8 的问题

[A-kirami]

这个 PR 带来了什么样的更改？

• [x] 错误修复
• [ ] 新功能
• [ ] 文档/注释
• [ ] 代码格式
• [ ] 代码重构
• [ ] 测试用例
• [ ] 性能优化
• [ ] 外观样式
• [ ] 项目构建
• [ ] 依赖环境
• [ ] 持续集成/部署
• [ ] 其他，请描述:

这个 PR 是否存在破坏性变更？

• [ ] 是的，并已在 issue #___ 号中获得批准
• [x] 没有

描述

修复类型注解与项目要求版本不匹配的问题

动机和背景

resolve #14

其他信息

检查工作

• [x] 我对我的代码进行了注释，特别是在难以理解的部分
• [x] 我的更改需要更新文档，并且已对文档进行了相应的更改
• [x] 我添加了测试并且已经在本地通过，以证明我的修复补丁或新功能有效
• [x] 我已检查并确保更改没有与其他打开的 Pull Requests 重复

[sourcery-ai[bot]]

Sourcery Code Quality Report

Merging this PR leaves code quality unchanged.

Quality metrics	Before	After	Change
Complexity	1.00 ⭐	1.00 ⭐	0.00
Method Length	28.17 ⭐	28.17 ⭐	0.00
Working memory	3.38 ⭐	3.38 ⭐	0.00
Quality	90.81% ⭐	90.81% ⭐	0.00%

Other metrics	Before	After	Change
Lines	26	26	0

Changed files	Quality Before	Quality After	Quality Change
nonebot_plugin_aidraw/limit.py	90.81% ⭐	90.81% ⭐	0.00%

Here are some functions in these files that still need a tune-up:

File	Function	Complexity	Length	Working Memory	Quality	Recommendation

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