fix-flex #1532

[pingan1927]

First of all, thank you for your contribution! :-)

Please makes sure that these checkboxes are checked before submitting your PR, thank you!

• Make sure that you follow antd's code convention.
• Run npm run lint and fix those errors before submitting in order to keep consistent code style.
• Rebase before creating a PR to keep commit history clear.
• Add some descriptions and refer relative issues for you PR.

Extra checklist:

if isBugFix :

• Make sure that you add at least one unit test for the bug which you had fixed.

elif isNewFeature :

• Update API docs for the component.
• Update/Add demo to demonstrate new feature.
• Update TypeScript definition for the component.
• Add unit tests for the feature.

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This change is 

[mention-bot]

@pingan1927, thanks for your PR! By analyzing the history of the files in this pull request, we identified @paranoidjk, @warmhug and @silentcloud to be potential reviewers.

[warmhug]

就只改了文档、不改代码？

[paranoidjk]

ref #1532

Api 是 break change，放 2.0 改，这里只是优化文档

[pingan1927]

API再单独改