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[bot]]

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

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

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

Additional details and impacted files

```diff @@ 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 ```

:umbrella: View full report in Codecov by Sentry.
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[github-actions[bot]]

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[bot]]

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}