fix: Menu SubMenu background in dark theme

[afc163]

[中文版模板 / Chinese template]

🤔 This is a ...

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

🔗 Related issue link

close #25202

💡 Background and solution

ref #24997

#	Pic
Before ❌
After ✅

📝 Changelog

Language	Changelog
🇺🇸 English	Fix Menu.SubMenu background color in dark theme.
🇨🇳 Chinese	修复 Menu theme="dark" 时子菜单背景色为白色的问题。

☑️ 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

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View rendered components/menu/demo/horizontal.md
View rendered components/menu/demo/theme.md

[ant-design-bot]

[ant-design-bot]

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[codesandbox-ci]

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[codecov]

Codecov Report

Merging #25205 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #25205   +/-   ##
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  Coverage   99.43%   99.43%           
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  Files         365      365           
  Lines        7302     7302           
  Branches     1993     2034   +41     
=======================================
  Hits         7261     7261           
  Misses         41       41           

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