fix(Button): onClick type

[guoyunhe]

函数的返回类型用 void | Promise<void> 就够了，再或一个 unknown 是不必要的，在某些 eslint 规则下会报错。

[github-actions]

PR preview has been successfully built and deployed to https://antd-mobile-preview-pr-6588.surge.sh

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.34%. Comparing base (cf550e4) to head (1676535).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #6588   +/-   ##
=======================================
  Coverage   92.34%   92.34%           
=======================================
  Files         318      318           
  Lines        6910     6910           
  Branches     1729     1729           
=======================================
  Hits         6381     6381           
  Misses        493      493           
  Partials       36       36           

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[github-actions]

size-limit report 📦

Path	Size	Loading time (3g)	Running time (snapdragon)	Total time
./lib/bundle/antd-mobile.es.js	137.36 KB	2.8 s (0%)	1.4 s (+3.37% 🔺)	4.1 s

[github-actions]

Size Change: 0 B

Total Size: 353 kB

ℹ️ View Unchanged

Filename	Size
./lib/bundle/antd-mobile.compatible.umd.js	189 kB
./lib/bundle/antd-mobile.umd.js	144 kB
./lib/bundle/css-vars-patch.css	1.43 kB
./lib/bundle/style.css	18 kB

_{compressed-size-action}