fix: text add btn color in dark mode

[zombieJ]

[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
• Performance optimization
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🔗 Related issue link

fix #39717

💡 Background and solution

📝 Changelog

Language	Changelog
🇺🇸 English	Fix Tabs add button color invisible in dark mode.
🇨🇳 Chinese	修复 Tabs 添加按钮在暗色模式下不可见的问题。

☑️ Self-Check before Merge

⚠️ Please check all items below before requesting a reviewing. ⚠️

• 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

[github-actions]

[github-actions]

size-limit report 📦

Path	Size
./dist/antd.min.js	377.56 KB (+6 B 🔺)
./dist/antd-with-locales.min.js	432.86 KB (+7 B 🔺)

[codecov]

Codecov Report

Base: 100.00% // Head: 100.00% // No change to project coverage 👍

Coverage data is based on head (f6ef7b2) compared to base (9f18f76).
Patch has no changes to coverable lines.

Additional details and impacted files

@@            Coverage Diff            @@
##            master    #39724   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          556       556           
  Lines         9625      9625           
  Branches      2722      2722           
=========================================
  Hits          9625      9625           

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