fix(module:nzHighlight pipe): node title html parse issue #6477

[EnochGao]

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?

when node title is <axxx>title, node title will only display title

Issue Number: #6477

What is the new behavior?

display <axxx>title

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 91.82%. Comparing base (c3ab3ba) to head (35e74de).
Report is 33 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8898      +/-   ##
==========================================
- Coverage   91.84%   91.82%   -0.02%     
==========================================
  Files         548      548              
  Lines       19305    19305              
  Branches     2862     2862              
==========================================
- Hits        17730    17727       -3     
- Misses       1260     1262       +2     
- Partials      315      316       +1     

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