feat(module: calendar): update testing coverage

[3fuyu]

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-mobile/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
[x] 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

[codecov]

Codecov Report

Merging #474 into master will increase coverage by 1.68%.
The diff coverage is 85.71%.

@@            Coverage Diff             @@
##           master     #474      +/-   ##
==========================================
+ Coverage   85.83%   87.51%   +1.68%     
==========================================
  Files         270      270              
  Lines        7576     7579       +3     
  Branches     1076     1078       +2     
==========================================
+ Hits         6503     6633     +130     
+ Misses        656      530     -126     
+ Partials      417      416       -1

Impacted Files	Coverage Δ
...onents/calendar/datepicker/datepicker.component.ts	83.14% <100%> (+24.71%)	⬆️
components/calendar/calendar.component.ts	84.03% <80%> (+12.6%)	⬆️
components/picker/picker.component.ts	69% <0%> (+1.5%)	⬆️
components/calendar/header/header.component.ts	88% <0%> (+4%)	⬆️
components/picker/picker.service.ts	85% <0%> (+5%)	⬆️
.../calendar/confirm-panel/confirm-panel.component.ts	95% <0%> (+10%)	⬆️
...s/calendar/datepicker/datepicker.base.component.ts	85.88% <0%> (+23.92%)	⬆️
...ts/calendar/single-month/single-month.component.ts	93.18% <0%> (+28.4%)	⬆️
... and 1 more

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[BronzeCui]

this._delta = event.touches[0].screenY || event.touches[0].pageY - this._lastY;
check this

[BronzeCui]

change title: test(module: calendar).....