fix(module:tabs): keyboard events in extra areas trigger navigation

[hsuanxyz]

close #6139

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: #6139

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[zorro-bot]

This preview will be available after the AzureCI is passed.

[codecov]

Codecov Report

Merging #6173 (e5a075d) into master (083ed4d) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #6173      +/-   ##
==========================================
+ Coverage   89.85%   89.87%   +0.01%     
==========================================
  Files         468      468              
  Lines       14255    14256       +1     
  Branches     2242     2242              
==========================================
+ Hits        12809    12812       +3     
+ Misses        891      890       -1     
+ Partials      555      554       -1     

Impacted Files	Coverage Δ
components/tabs/tab-nav-bar.component.ts	83.09% <100.00%> (+0.76%)	⬆️
components/alert/alert.component.ts	94.44% <0.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 083ed4d...e5a075d. Read the comment docs.