Modify typos in why.md files

[huyikai]

Related ISSUE

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Type Of Change

• [ ] 🐞 Bug fix (non-breaking change which fixes an issue)
• [ ] ✨ New feature (non-breaking change which adds functionality)
• [x] 📝 Document (This change requires a documentation update)
• [ ] 🎨 Theme style (Theme style beautification)
• [ ] ⚠ Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] 🔨 Workflow (Workflow changes)

Clear Describe

Modify Text：是→式

Description

When viewing the document, I saw typos and corrected them accordingly

Test Case

none

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🔨 Latest commit	67b71c800acdef4bb4a3e44fb2064627db83024f

[Zhengqbbb]

Thx~