fix onFinish get full value instead of filtered one

[zombieJ]

fix ant-design/ant-design#21701

[vercel]

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[codecov]

Codecov Report

Merging #90 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master      #90   +/-   ##
=======================================
  Coverage   99.87%   99.87%           
=======================================
  Files          13       13           
  Lines         805      805           
  Branches      169      171    +2     
=======================================
  Hits          804      804           
  Misses          1        1

Impacted Files	Coverage Δ
src/useForm.ts	99.63% <100%> (ø)	⬆️
src/Form.tsx	100% <100%> (ø)	⬆️

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