fix(module:nz-input): cannot be disabled if ngModel is missing (#4655)

[zhytang]

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: #4655

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[zorro-bot]

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[codecov]

Codecov Report

Merging #4688 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #4688      +/-   ##
==========================================
+ Coverage   93.17%   93.18%   +<.01%     
==========================================
  Files         507      507              
  Lines       12779    12787       +8     
  Branches     2024     2026       +2     
==========================================
+ Hits        11907    11915       +8     
  Misses        455      455              
  Partials      417      417

Impacted Files	Coverage Δ
components/input/nz-input.directive.ts	100% <100%> (ø)	⬆️

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[vthinkxie]

Hi @zhytang
thanks for your PR, this issue is caused by angular, and fixed by angular v9 now, closing now