fix(NumberKeyboard): customKey background-color when dark

[YunYouJun]

Fix NumberKeyboard customKey background-color when dark mode,

Before:

After:

[codecov]

Codecov Report

Base: 89.44% // Head: 89.55% // Increases project coverage by +0.11% 🎉

Coverage data is based on head (b35d515) compared to base (0316cf8).
Patch has no changes to coverable lines.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5685      +/-   ##
==========================================
+ Coverage   89.44%   89.55%   +0.11%     
==========================================
  Files         296      296              
  Lines        6327     6327              
  Branches     1551     1551              
==========================================
+ Hits         5659     5666       +7     
+ Misses        618      612       -6     
+ Partials       50       49       -1     

Impacted Files	Coverage Δ
src/components/image-uploader/image-uploader.tsx	92.72% <0.00%> (+6.36%)	⬆️

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[github-actions]

PR preview has been successfully built and deployed to https://antd-mobile-preview-pr-5685.surge.sh