refactor(scripts): fix script about update less variable

[typistZxd]

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

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Component style update
• 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?

组件文档中如果less变量部分下方还有其他章节，如components/form/docs/index.zh.md 会导致脚本执行卡死

What is the new behavior?

即使有其他章节也能正常生成插入less变量

Other information

[idux-bot]

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[codecov]

Codecov Report

Merging #781 (eb99f10) into main (3d1f3fe) will not change coverage.
The diff coverage is n/a.

❗ Current head eb99f10 differs from pull request most recent head 11092ed. Consider uploading reports for the commit 11092ed to get more accurate results

@@           Coverage Diff           @@
##             main     #781   +/-   ##
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  Coverage   83.96%   83.96%           
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  Files         465      465           
  Lines       12034    12034           
  Branches     2891     2891           
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  Hits        10104    10104           
  Misses       1930     1930           

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