fix: fix cascader onChange type

[MadCcc]

close #234


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[codecov]

Codecov Report

Merging #236 (a86b63a) into master (9f9fc20) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #236   +/-   ##
=======================================
  Coverage   99.78%   99.78%           
=======================================
  Files          15       15           
  Lines         466      466           
  Branches      117      123    +6     
=======================================
  Hits          465      465           
  Misses          1        1           

Impacted Files	Coverage Δ
src/Cascader.tsx	100.00% <ø> (ø)

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