fix(comp:modal): the size of button should be 'md'

[danranVm]

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?

• Seer 主题下，Modal 的按钮默认为 ’sm‘

What is the new behavior?

• 改为 md

Other information

[idux-bot]

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[codecov]

Codecov Report

Merging #1582 (748a2e0) into main (ab4e4b0) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 748a2e0 differs from pull request most recent head 1c5e4f5. Consider uploading reports for the commit 1c5e4f5 to get more accurate results

@@           Coverage Diff            @@
##             main    #1582    +/-   ##
========================================
  Coverage   92.76%   92.76%            
========================================
  Files         332      332            
  Lines       30695    30699     +4     
  Branches     3510     2568   -942     
========================================
+ Hits        28473    28477     +4     
  Misses       2222     2222            

Impacted Files	Coverage Δ
packages/components/icon/src/dependencies.ts	99.18% <100.00%> (+0.01%)	⬆️
packages/components/modal/src/ModalWrapper.tsx	79.53% <100.00%> (+0.10%)	⬆️