fix #fff border in text button when apply ghost mode

[bahram-azimbeyk]

PR Checklist

Please check if your PR fulfills the following requirements:

• [x] The commit message follows our guidelines: https://github.com/NG-ZORRO/ng-zorro-antd/blob/master/CONTRIBUTING.md#commit
• [x] 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

For this code:

Before:

After:

[zorro-bot[bot]]

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[codecov[bot]]

Codecov Report

Merging #8021 (41800a5) into master (078aaf9) will increase coverage by 0.02%. The diff coverage is n/a.

:exclamation: Current head 41800a5 differs from pull request most recent head 5fa5273. Consider uploading reports for the commit 5fa5273 to get more accurate results

@@            Coverage Diff             @@
##           master    #8021      +/-   ##
==========================================
+ Coverage   91.65%   91.67%   +0.02%     
==========================================
  Files         515      515              
  Lines       17641    17641              
  Branches     2790     2790              
==========================================
+ Hits        16168    16172       +4     
+ Misses       1175     1169       -6     
- Partials      298      300       +2     

see 1 file with indirect coverage changes

[Laffery]

Good first issue! Should be consistent with ant design, there is a border when hovering on the button.

[Nicoss54]

@bahram-azimbeyk changes are not made yet, could you apply the requested change please ? :)