fix(module:pagination): add space between page size and slash

[oestrogen]

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: #4038

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 #4039 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #4039   +/-   ##
=======================================
  Coverage   92.18%   92.18%           
=======================================
  Files         520      520           
  Lines       10991    10991           
  Branches     1990     1990           
=======================================
  Hits        10132    10132           
  Misses        430      430           
  Partials      429      429

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[wzhudev]

@oestrogen Thanks for your pull request! Please edit your commit message. Refer to our contributing guide.

[oestrogen]

@wendzhue I have now changed the commit message according to the guide. Thanks for the patience! 😊

[vthinkxie]

LGTM