fix(module:select): cursor abnormal in nz-select with nzDisabled

[Eve-Sama]

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
[x] Documentation content changes
[ ] Application (the showcase website) / infrastructure changes
[ ] Other... Please describe:

What is the current behavior?

Issue Number: #5709

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[Eve-Sama]

上图是 #5709 issue所提供的复现场景的计算属性, 显示cursor的not-allowed被text覆盖了. 显然当nzDisabled为true时不应该添加这个样式, 所以我在[class.ant-select-show-search]的判断上增加了nzDisabled的判断.

[codecov]

Codecov Report

Merging #5716 into master will decrease coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #5716      +/-   ##
==========================================
- Coverage   90.09%   90.07%   -0.03%     
==========================================
  Files         455      455              
  Lines       13798    13798              
  Branches     2183     2183              
==========================================
- Hits        12431    12428       -3     
- Misses        843      844       +1     
- Partials      524      526       +2     

Impacted Files	Coverage Δ
components/select/select.component.ts	87.50% <ø> (ø)
components/core/util/text-measure.ts	89.56% <0.00%> (-1.74%)	⬇️
components/time-picker/time-holder.ts	94.73% <0.00%> (-1.06%)	⬇️

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