fix(module:date-picker): replace DatePipe with formatDate function

[wenqi73]

PR Checklist

Close #3487
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: N/A

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

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[codecov]

Codecov Report

Merging #3500 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master   #3500      +/-   ##
=========================================
- Coverage    95.6%   95.6%   -0.01%     
=========================================
  Files         609     609              
  Lines       13250   13247       -3     
  Branches     1810    1810              
=========================================
- Hits        12668   12665       -3     
  Misses        197     197              
  Partials      385     385

Impacted Files	Coverage Δ
components/i18n/nz-i18n.module.ts	100% <ø> (ø)	⬆️
components/i18n/date-helper.service.ts	84.78% <100%> (-0.64%)	⬇️

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[wzhudev]

LGTM