fix(module:icon): fix old icon element not removed

[wzhudev]

close #7186

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: N/A

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[ ] No

Other information

[zorro-bot]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.65%. Comparing base (77db914) to head (66b3a6b).
Report is 766 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7188      +/-   ##
==========================================
- Coverage   91.67%   91.65%   -0.02%     
==========================================
  Files         486      486              
  Lines       15868    15870       +2     
  Branches     2587     2587              
==========================================
- Hits        14547    14546       -1     
- Misses       1007     1009       +2     
- Partials      314      315       +1     

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