fix(module:menu): fix menu level 4 padding error

[vthinkxie]

close #2327

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/NG-ZORRO/ng-zorro-antd/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[x] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Application (the showcase website) / infrastructure changes
[ ] Other... Please describe:

What is the current behavior?

Issue Number: N/A

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[codecov]

Codecov Report

Merging #2356 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #2356      +/-   ##
==========================================
+ Coverage   95.85%   95.86%   +<.01%     
==========================================
  Files         485      485              
  Lines       12231    12228       -3     
  Branches     1645     1644       -1     
==========================================
- Hits        11724    11722       -2     
  Misses        149      149              
+ Partials      358      357       -1

Impacted Files	Coverage Δ
components/menu/nz-submenu.component.ts	95.45% <100%> (+0.63%)	⬆️

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