docs(module:layout): fix responsive demo

[hsuanxyz]

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
[x] 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

[netlify]

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[codecov]

Codecov Report

Merging #2566 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master   #2566   +/-   ##
======================================
  Coverage    95.5%   95.5%           
======================================
  Files         495     495           
  Lines       12098   12098           
  Branches     1689    1689           
======================================
  Hits        11554   11554           
  Misses        172     172           
  Partials      372     372

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