fix(module:button): add ant-btn-default class

[HyperLife1119]

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

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.59%. Comparing base (55cbf18) to head (91d7fe1).
Report is 1 commits behind head on master.

Additional details and impacted files

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  Coverage   91.59%   91.59%           
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  Files         533      533           
  Lines       18329    18329           
  Branches     2797     2797           
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  Hits        16788    16788           
  Misses       1225     1225           
  Partials      316      316           

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[OriginRing]

当前并没有这个class样式，添加它是解决什么问题吗？当然这个 pr 是正常的。

[HyperLife1119]

在标准 AntDesign 组件中是有这个 class 的：

尽管在 antd 4 中，这只是一个没有样式的 class，但在 antd 5 中，它获得了样式：

[OriginRing]

LGTM