fix: submenu disalbed style

[skyline-123]

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This is a ...

• New feature
• Bug fix
• Site / document update
• Component style update
• TypeScript definition update
• Refactoring
• Code style optimization
• Branch merge
• Other (about what?)

What's the background?

1. Describe the source of requirement.
   The style of submenus for cascading menu is wrong.
2. Resolve what problem.
   Fix the disabled status of submenus for cascading menu.
3. Related issue link.

API Realization (Optional if not new feature)

1. Basic thought of solution and other optional proposal.
2. List final API realization and usage sample.
3. GIF or snapshot should be provided if includes UI/interactive modification.

What's the effect? (Optional if not new feature)

1. Does this PR affect user? Which part will be affected?
2. What will say in changelog?
3. Does this PR contains potential break change or other risk?

Changelog description (Optional if not new feature)

1. English description
2. Chinese description (optional)

Self Check before Merge

• Doc is updated/provided or not needed
• Demo is updated/provided or not needed
• TypeScript definition is updated/provided or not needed
• Changelog is provided or not needed

Additional Plan? (Optional if not new feature)

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[codecov]

Codecov Report

Merging #921 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #921   +/-   ##
=======================================
  Coverage   87.27%   87.27%           
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  Files         145      145           
  Lines        4817     4817           
  Branches     1421     1421           
=======================================
  Hits         4204     4204           
  Misses        570      570           
  Partials       43       43

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[github-actions]

This pull request has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.