fix(module:progress): fix circle gradient not sorted

[wzhudev]

close #4176

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: #4176

What is the new behavior?

Circle gradient stops would now be sorted.

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

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[codecov]

Codecov Report

Merging #4178 into master will increase coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #4178      +/-   ##
==========================================
+ Coverage   92.27%   92.29%   +0.02%     
==========================================
  Files         517      517              
  Lines       10962    10966       +4     
  Branches     1985     1985              
==========================================
+ Hits        10115    10121       +6     
+ Misses        422      421       -1     
+ Partials      425      424       -1

Impacted Files	Coverage Δ
components/progress/nz-progress.component.ts	95.87% <100%> (+0.13%)	⬆️
components/progress/nz-progress-utils.ts	90% <100%> (+11.05%)	⬆️

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