test: Update back-top test case

[hms181231]

[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
• Enhancement feature
• Internationalization
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• Code style optimization
• Test Case
• Branch merge
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💡 Background and solution

📝 Changelog

Language	Changelog
🇺🇸 English
🇨🇳 Chinese

☑️ 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
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[github-actions]

[codecov]

Codecov Report

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

Coverage data is based on head (0d9039c) compared to base (3eff12d).
Patch has no changes to coverable lines.

Additional details and impacted files

@@            Coverage Diff            @@
##            master    #38147   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          444       444           
  Lines         8217      8215    -2     
  Branches      2491      2490    -1     
=========================================
- Hits          8217      8215    -2     

Impacted Files	Coverage Δ
components/tree/utils/dictUtil.ts	100.00% <0.00%> (ø)

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