fix(dropdown): children type

[uyarn]

🤔 这个 PR 的性质是？

• 日常 bug 修复
• 新特性提交
• 文档改进
• 演示代码改进
• 组件样式/交互改进
• CI/CD 改进
• 重构
• 代码风格优化
• 测试用例
• 分支合并
• 其他

🔗 相关 Issue

💡 需求背景和解决方案

📝 更新日志

• fix(dropdown): 修复下拉菜单展开位置的异常

• 本条 PR 不需要纳入 Changelog

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⚠️ 请自检并全部勾选全部选项。⚠️

• 文档已补充或无须补充
• 代码演示已提供或无须提供
• TypeScript 定义已补充或无须补充
• Changelog 已提供或无须提供

[github-actions]

[codecov-commenter]

Codecov Report

Merging #1300 (fe6ab27) into develop (b249875) will increase coverage by 0.14%.
The diff coverage is 52.94%.

@@             Coverage Diff             @@
##           develop    #1300      +/-   ##
===========================================
+ Coverage    59.73%   59.87%   +0.14%     
===========================================
  Files         1007     1017      +10     
  Lines        17661    17805     +144     
  Branches      4032     4083      +51     
===========================================
+ Hits         10550    10661     +111     
- Misses        7111     7144      +33     

Impacted Files	Coverage Δ
src/cascader/Cascader.tsx	57.89% <0.00%> (ø)
src/date-picker/panel/RangePanel.tsx	82.22% <ø> (ø)
src/dropdown/Dropdown.tsx	81.48% <ø> (ø)
src/input-number/_example/center.jsx	44.44% <ø> (ø)
src/input-number/_example/large-number.jsx	100.00% <ø> (ø)
src/select/base/Select.tsx	72.31% <ø> (ø)
src/table/THead.tsx	92.85% <0.00%> (-2.27%)	⬇️
src/table/_example/affix.jsx	95.74% <ø> (ø)
src/tag-input/TagInput.tsx	63.79% <ø> (ø)
src/input/_example/size.jsx	33.33% <33.33%> (-9.53%)	⬇️
... and 24 more

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