fix(abc:st): fix can't addRow in group columns

[cipchk]

• close st表格，使用表头分组时，addRow(data: STData | STData[], options?: { index?: number })不能添加的问题 ng-alain#2532

PR Checklist

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• 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

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[cipchk]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.00%. Comparing base (983cedb) to head (9d8bb82).
Report is 5 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1871      +/-   ##
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- Coverage   95.00%   95.00%   -0.01%     
==========================================
  Files         273      273              
  Lines        8845     8843       -2     
  Branches     1705     1806     +101     
==========================================
- Hits         8403     8401       -2     
  Misses        364      364              
  Partials       78       78              

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