Update prompts.py：Fix conversation title language for Italian conversations

[zhangkun-21]

Summary

Added 'Italian' to the conversation title prompt to fix an issue where conversations conducted in Italian were incorrectly generating titles in Spanish.

This change ensures that when clients are having conversations in Italian, the generated conversation titles properly match the language of the conversation instead of defaulting to Spanish.

Tip

Close issue syntax: Fixes #<issue number> or Resolves #<issue number>, see documentation for more details.

Screenshots

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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