fix(module:auto-complete): default value not selected

[hsuanxyz]

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: #4362

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[netlify]

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[codecov]

Codecov Report

Merging #4366 into master will increase coverage by 0.02%.
The diff coverage is 93.93%.

@@            Coverage Diff             @@
##           master    #4366      +/-   ##
==========================================
+ Coverage    92.2%   92.23%   +0.02%     
==========================================
  Files         520      521       +1     
  Lines       11039    11094      +55     
  Branches     1997     2014      +17     
==========================================
+ Hits        10178    10232      +54     
- Misses        429      436       +7     
+ Partials      432      426       -6

Impacted Files	Coverage Δ
.../auto-complete/nz-autocomplete-option.component.ts	94.11% <100%> (+0.36%)	⬆️
...ponents/auto-complete/nz-autocomplete.component.ts	96.05% <100%> (+0.33%)	⬆️
...auto-complete/nz-autocomplete-trigger.directive.ts	94.73% <88.88%> (-1.3%)	⬇️
...mponents/carousel/strategies/transform-strategy.ts	84.81% <0%> (-10.13%)	⬇️
components/core/util/dom.ts	85.71% <0%> (-3.18%)	⬇️
components/core/tree/nz-tree-base.service.ts	93.62% <0%> (-0.4%)	⬇️
...ts/date-picker/lib/popups/inner-popup.component.ts	95.45% <0%> (-0.38%)	⬇️
components/carousel/nz-carousel.component.ts	93.12% <0%> (-0.12%)	⬇️
components/tree/nz-tree.component.ts	97.74% <0%> (-0.07%)	⬇️
components/page-header/nz-page-header.component.ts	100% <0%> (ø)	⬆️
... and 15 more

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[vthinkxie]

LGTM