Fix the style of horizontal menu on dark theme

[hongxuWei]

First of all, thank you for your contribution! :-)

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if isBugFix :

• Make sure that you add at least one unit test for the bug which you had fixed.

elif isNewFeature :

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[hongxuWei]

issue link

[ant-design-bot]

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[codecov]

Codecov Report

Merging #11400 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #11400   +/-   ##
=======================================
  Coverage   91.76%   91.76%           
=======================================
  Files         199      199           
  Lines        5014     5014           
  Branches     1403     1403           
=======================================
  Hits         4601     4601           
  Misses        408      408           
  Partials        5        5

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