fix: Remove the default value of the empty string

[thinkasany]

[中文版模板 / Chinese template]

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🔗 Related issue link

💡 Background and solution

1. className 都是可选类型 可以是undefined不需要给默认值

2. classNames 函数的参数列表中包括了空字符串 ''，但是它会被忽略

📝 Changelog

Language	Changelog
🇺🇸 English	Remove the default value of the empty string
🇨🇳 Chinese	去掉空字符串的默认值

☑️ 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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🚀 Summary

🤖 Generated by Copilot at 47f72cb

This pull request refactors some components to simplify code and follow import conventions. It also removes unnecessary default values of className props in Anchor and CollapsePanel components.

🔍 Walkthrough

🤖 Generated by Copilot at 47f72cb

• Remove default values of className prop in Anchor, CollapsePanel, and Group components to simplify code and avoid conflicts (link, link, link)
• Reorder import statements in Group component to follow convention of React and hooks first, then external modules, then internal modules (link)

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