fix(module:breadcrumb): fix breadcrumb link style

[wzhudev]

close #4855

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

[zorro-bot]

This preview will be available after the AzureCI is passed.

[codecov]

Codecov Report

Merging #4880 into master will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4880      +/-   ##
==========================================
+ Coverage   92.93%   92.94%   +0.01%     
==========================================
  Files         505      506       +1     
  Lines       12718    12750      +32     
  Branches     1963     1965       +2     
==========================================
+ Hits        11819    11851      +32     
  Misses        474      474              
  Partials      425      425              

Impacted Files	Coverage Δ
...omponents/date-picker/abstract-picker.component.ts	94.96% <0.00%> (-0.11%)	⬇️
components/date-picker/date-picker.service.ts	100.00% <0.00%> (ø)
components/skeleton/nz-skeleton.module.ts
components/skeleton/nz-skeleton.component.ts
components/skeleton/skeleton.component.ts	100.00% <0.00%> (ø)
components/skeleton/skeleton-element.component.ts	100.00% <0.00%> (ø)
components/skeleton/skeleton.module.ts	100.00% <0.00%> (ø)
...mponents/date-picker/date-range-popup.component.ts	91.87% <0.00%> (+0.08%)	⬆️
components/date-picker/lib/year-table.component.ts	95.12% <0.00%> (+0.12%)	⬆️
components/date-picker/picker.component.ts	94.11% <0.00%> (+0.21%)	⬆️
... and 1 more

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