feat: 补充 FormItem 文档 getValueProps 接口额外说明

[LongHaoo]

[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
• Refactoring
• Code style optimization
• Test Case
• Branch merge
• Workflow
• Other (about what?)

🔗 Related issue link

关联 PR #46445
关联 issue #46417

💡 Background and solution

优化文档 Form.Item getValueProps 的解释

📝 Changelog

Language	Changelog
🇺🇸 English	Optimize the explanation of documentation Form.Item getValueProps
🇨🇳 Chinese	优化文档 Form.Item getValueProps 的解释

☑️ 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
• TypeScript definition is updated/provided or not needed
• Changelog is provided or not needed

[stackblitz]

Run & review this pull request in StackBlitz Codeflow.

[github-actions]

[codesandbox-ci]

This pull request is automatically built and testable in CodeSandbox.

To see build info of the built libraries, click here or the icon next to each commit SHA.

Latest deployment of this branch, based on commit 8388f4d:

Sandbox	Source
antd reproduction template (forked)	Configuration

[github-actions]

Visual Regression Report for PR #46485 Passed ✅

Target branch: master (49e6045)

---

Congrats! No visual-regression diff found

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (49e6045) 100.00% compared to head (8388f4d) 100.00%.

Additional details and impacted files

@@            Coverage Diff            @@
##            master    #46485   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          708       708           
  Lines        12120     12120           
  Branches      3217      3217           
=========================================
  Hits         12120     12120           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.