Fix typo in Slider Documentation

[AbdullahAnsarii]

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

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

• [x] Make sure that you follow antd's code convention.
• [x] Run npm run lint and fix those errors before submitting in order to keep consistent code style.
• [x] Rebase before creating a PR to keep commit history clear.
• [x] 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.

[1uokun]

How do you Do it bro? Amazing🧐

[AbdullahAnsarii]

@1uokun Lol, Hire me as your documentation reviewer

[1uokun]

patch-2 branch was deleted bro, I need your code

[AbdullahAnsarii]

@1uokun I have reopened the pull request

[1uokun]

Are you interested in an automatic typo detection? Like textlint

[AbdullahAnsarii]

Sure, it looks good