fix: mp3 file upload not work

[hjlarry]

Checklist:

Important

Please review the checklist below before submitting your pull request.

• Please open an issue before creating a PR or link to an existing issue
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods

Description

Fixes #10644

when you upload a mp3 file, the fileMimetype is audio/mpeg, and the extension in the frontend is mpga

The LLM told me mpga is another format of mp3, not any format of VIDEO, but I can't find any reliable source of this thing, so I haven't remove it from video extension.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update, included: Dify Document
• Improvement, including but not limited to code refactoring, performance optimization, and UI/UX improvement
• Dependency upgrade

Testing Instructions

test locally.

• Test A
• Test B