Fix: 修复 ArgumentParser 错误信息叠加问题

[yanyongyu]

fix #1425

[github-actions]

🚀 Deployed on https://deploy-preview-1426--nonebot2.netlify.app

[codecov]

Codecov Report

Merging #1426 (f32b313) into master (6c27ec7) will decrease coverage by 0.00%.
The diff coverage is 87.50%.

@@            Coverage Diff             @@
##           master    #1426      +/-   ##
==========================================
- Coverage   85.70%   85.69%   -0.01%     
==========================================
  Files          44       44              
  Lines        3301     3306       +5     
==========================================
+ Hits         2829     2833       +4     
- Misses        472      473       +1     

Flag	Coverage Δ
unittests	85.69% <87.50%> (-0.01%)	⬇️

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Impacted Files	Coverage Δ
nonebot/rule.py	97.44% <87.50%> (-0.33%)	⬇️

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