docs: fix rlt mode change range value error

[jiandan1989]

• 修复 rlt 示例 RangePicker onChange 错误
• 设置 defaultValue 为当前时间

[vercel]

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Name	Status	Preview	Updated
picker	✅ Ready (Inspect)	Visit Preview	May 22, 2022 at 10:00AM (UTC)

[codecov]

Codecov Report

Merging #410 (d162d91) into master (5306c89) will not change coverage.
The diff coverage is n/a.

❗ Current head d162d91 differs from pull request most recent head cc0f8de. Consider uploading reports for the commit cc0f8de to get more accurate results

@@           Coverage Diff           @@
##           master     #410   +/-   ##
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  Coverage   99.53%   99.53%           
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  Files          46       46           
  Lines        2150     2150           
  Branches      643      643           
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  Hits         2140     2140           
  Misses          8        8           
  Partials        2        2           

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