fix(form): update ReturnType<SearchConvertKeyFn>

[q1uxu]

ProFormField的前置转化propconvertValue 的类型SearchConvertKeyFn支持返回boolean类型。
因为ProFormCheckbox组件的value值是boolean类型，所以convertValue 返回的值按理来说应该要支持boolean值。

[github-actions]

🎊 PR Preview has been successfully built and deployed to https://pro-components-preview-pr-7462.surge.sh

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (6ead3b1) 98.33% compared to head (338653e) 98.33%.
Report is 2 commits behind head on master.

❗ Current head 338653e differs from pull request most recent head 88336c5. Consider uploading reports for the commit 88336c5 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #7462   +/-   ##
=======================================
  Coverage   98.33%   98.33%           
=======================================
  Files         339      339           
  Lines       11343    11343           
  Branches     4132     4132           
=======================================
  Hits        11154    11154           
  Misses        154      154           
  Partials       35       35           

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