fix: #24458 @tree-directory-selected-bg don't work

[morenyang]

[中文版模板 / Chinese template]

close #24458

🤔 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

• @tree-directory-selected-bg 无效 #24458

💡 Background and solution

• replace variable with @tree-directory-selected-bg

📝 Changelog

Language	Changelog
🇺🇸 English	fix @tree-directory-selected-bg don't work.
🇨🇳 Chinese	修复 @tree-directory-selected-bg 变量不生效的问题。

☑️ 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]

[ant-design-bot]

[codecov]

Codecov Report

Merging #24468 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #24468   +/-   ##
=======================================
  Coverage   99.04%   99.04%           
=======================================
  Files         363      363           
  Lines        7261     7261           
  Branches     2009     2009           
=======================================
  Hits         7192     7192           
  Misses         69       69           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update ccd2820...966daa3. Read the comment docs.