test(module:calendar): change expected class name

[wenqi73]

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

[codecov]

Codecov Report

Merging #4369 into master will increase coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           master   #4369      +/-   ##
=========================================
+ Coverage    92.2%   92.2%   +<.01%     
=========================================
  Files         520     520              
  Lines       11039   11039              
  Branches     1997    1997              
=========================================
+ Hits        10178   10179       +1     
  Misses        429     429              
+ Partials      432     431       -1

Impacted Files	Coverage Δ
components/dropdown/nz-dropdown.component.ts	95.83% <0%> (+2.08%)	⬆️

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