fix(module:tabs): fix selected index not updated

[wzhudev]

close #3873

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: #3873

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[netlify]

Deploy preview for ng-zorro-master ready!

Built with commit a5fca54

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[codecov]

Codecov Report

Merging #4094 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master   #4094      +/-   ##
=========================================
+ Coverage    92.4%   92.4%   +<.01%     
=========================================
  Files         506     506              
  Lines       10758   10759       +1     
  Branches     1940    1940              
=========================================
+ Hits         9941    9942       +1     
  Misses        402     402              
  Partials      415     415

Impacted Files	Coverage Δ
components/tabs/nz-tabset.component.ts	91.8% <100%> (+0.06%)	⬆️

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