fix: Menu duplicated shadow style

[afc163]

🤔 This is a ...

• New feature
• Bug fix
• Site / document update
• Component style update
• TypeScript definition update
• Refactoring
• Code style optimization
• Test Case
• Branch merge
• Other (about what?)

🔗 Related issue link

close #23625

💡 Background and solution

📝 Changelog

Language	Changelog
🇺🇸 English	Fix Menu duplicated shadow style.
🇨🇳 Chinese	修复 Menu 菜单重复阴影的问题。

☑️ Self Check before Merge

⚠️ Please check all items below before review. ⚠️

• Doc is updated/provided or not needed
• Demo is updated/provided or not needed
• TypeScript definition is updated/provided or not needed
• Changelog is provided or not needed

[ant-design-bot]

[afc163]

比想象的好改很多。

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[codecov]

Codecov Report

Merging #23664 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #23664   +/-   ##
=======================================
  Coverage   98.49%   98.49%           
=======================================
  Files         363      363           
  Lines        7197     7197           
  Branches     1990     2000   +10     
=======================================
  Hits         7089     7089           
  Misses        108      108           

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