chore(lint): correct allowed-unused-imports settings for cleanup unused imports in tests

[bowenliang123]

Summary

• correct extend-generics settings to allowed-unused-imports for removing unused imports in tests

Screenshots

Before	After
...	...

Checklist

Important

Please review the checklist below before submitting your pull request.

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods

[bowenliang123]

cc @laipz8200

[laipz8200]

Thanks!