fix(module:steps): remove top-level redundant div element

[HyperLife1119]

The first div child of the nz-steps element is redundant and should be merged with the nz-steps element.

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?

There is a layer of redundant div element under the nz-steps element.

Issue Number: N/A

What is the new behavior?

Remove redundant div element.

Does this PR introduce a breaking change?

[x] Yes
[ ] No

I'm not sure if this introduces breaking changes, but this changes the existing DOM structure.

Other information

[codecov]

Codecov Report

Merging #7582 (a21c380) into master (f18149a) will decrease coverage by 0.00%.
The diff coverage is n/a.

❗ Current head a21c380 differs from pull request most recent head 355a788. Consider uploading reports for the commit 355a788 to get more accurate results

@@            Coverage Diff             @@
##           master    #7582      +/-   ##
==========================================
- Coverage   91.74%   91.73%   -0.01%     
==========================================
  Files         502      502              
  Lines       16756    16746      -10     
  Branches     2757     2755       -2     
==========================================
- Hits        15372    15362      -10     
  Misses       1050     1050              
  Partials      334      334              

Impacted Files	Coverage Δ
components/steps/demo/nav.ts	50.00% <ø> (ø)
components/steps/steps.component.ts	100.00% <ø> (ø)

Help us with your feedback. Take ten seconds to tell us how you rate us.

[hsuanxyz]

LGTM, but there has been a breaking change, just like the following screenshot, if someone used the display attribute to nz-steps his style will be broken. I suggest to merge it in v14.

[HyperLife1119]

I just fixed the demo, do I need to point this PR to the v14 branch?

[hsuanxyz]

thx, no, I'll label it.