fix(module:cascader): fix dynamic loading error

[wzhudev]

close #1927

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: #1927

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[codecov]

Codecov Report

Merging #1931 into master will increase coverage by 0.01%.
The diff coverage is 96.29%.

@@            Coverage Diff            @@
##           master   #1931      +/-   ##
=========================================
+ Coverage   95.98%     96%   +0.01%     
=========================================
  Files         470     470              
  Lines       11393   11404      +11     
  Branches     1508    1511       +3     
=========================================
+ Hits        10936   10948      +12     
  Misses        131     131              
+ Partials      326     325       -1

Impacted Files	Coverage Δ
components/cascader/nz-cascader.component.ts	96.55% <96.29%> (+0.24%)	⬆️

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