fix(module:drawer): style error when the unit is percentage

[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?

[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: #2333

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[codecov]

Codecov Report

Merging #2334 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #2334      +/-   ##
==========================================
+ Coverage   95.85%   95.86%   +0.01%     
==========================================
  Files         485      485              
  Lines       12215    12224       +9     
  Branches     1647     1645       -2     
==========================================
+ Hits        11709    11719      +10     
  Misses        148      148              
+ Partials      358      357       -1

Impacted Files	Coverage Δ
components/drawer/nz-drawer.component.ts	98.19% <100%> (+0.74%)	⬆️

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