fix(module:form): fix form overlap

[vthinkxie]

close #3607

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?

[ ] 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: N/A

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[ ] No

Other information

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[codecov]

Codecov Report

Merging #3633 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #3633      +/-   ##
==========================================
+ Coverage   95.46%   95.46%   +<.01%     
==========================================
  Files         685      685              
  Lines       14080    14081       +1     
  Branches     1874     1875       +1     
==========================================
+ Hits        13442    13443       +1     
  Misses        226      226              
  Partials      412      412

Impacted Files	Coverage Δ
components/form/nz-form-control.component.ts	93.61% <100%> (+0.06%)	⬆️

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