fix(module:tree): stop drop event change url in firefox

[stygian-desolator]

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

close #6730
close #6526
close #5807

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 #6771 (5911423) into master (1ec3f64) will decrease coverage by 0.17%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #6771      +/-   ##
==========================================
- Coverage   89.88%   89.71%   -0.18%     
==========================================
  Files         479      484       +5     
  Lines       15489    15667     +178     
  Branches     2522     2553      +31     
==========================================
+ Hits        13923    14056     +133     
- Misses        943      973      +30     
- Partials      623      638      +15     

Impacted Files	Coverage Δ
components/tree/tree-node.component.ts	90.16% <100.00%> (+0.10%)	⬆️
components/steps/steps.component.ts	91.13% <0.00%> (-5.79%)	⬇️
components/popconfirm/popconfirm.ts	96.00% <0.00%> (-4.00%)	⬇️
components/steps/step.component.ts	95.91% <0.00%> (-1.81%)	⬇️
components/table/src/table-style.service.ts	94.82% <0.00%> (-1.73%)	⬇️
components/time-picker/time-holder.ts	94.73% <0.00%> (-1.06%)	⬇️
components/core/config/config.ts	100.00% <0.00%> (ø)
components/steps/steps.module.ts	100.00% <0.00%> (ø)
components/popconfirm/popconfirm.module.ts	100.00% <0.00%> (ø)
components/image/image-preview.component.ts	90.13% <0.00%> (ø)
... and 11 more

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[hsuanxyz]

LGTM