fix(comp:button): button-group style error when nesting itself

[liuzaijiang]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines
• Tests for the changes have been added/updated or not needed
• Docs and demo have been added/updated or not needed

What is the current behavior?

button-group内部嵌套button-group时，子级会被父级样式影响

What is the new behavior?

Other information

[idux-bot]

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[codecov]

Codecov Report

Merging #1299 (a2a2c43) into main (6f77ada) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1299   +/-   ##
=======================================
  Coverage   93.04%   93.04%           
=======================================
  Files         322      322           
  Lines       29818    29818           
  Branches     3366     3366           
=======================================
  Hits        27743    27743           
  Misses       2075     2075           

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