fix: Tree switcher icon

[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 #20511

💡 Background and solution

📝 Changelog

Language	Changelog
🇺🇸 English	Fix Tree switcherIcon shown in leaf node problem.
🇨🇳 Chinese	修复 Tree switcherIcon 在叶子节点上展示的问题。

☑️ Self Check before Merge

• 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

[tests-checker]

Could you please add tests to make sure this change works as expected?

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[codecov]

Codecov Report

Merging #20753 into 3.x-stable will not change coverage.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           3.x-stable   #20753   +/-   ##
===========================================
  Coverage       97.81%   97.81%           
===========================================
  Files             286      286           
  Lines            7749     7749           
  Branches         2172     2138   -34     
===========================================
  Hits             7580     7580           
  Misses            169      169

Impacted Files	Coverage Δ
components/tree/Tree.tsx	96.66% <100%> (ø)	⬆️

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