deskutils/fet: update to 6.9.1

ChangeLog: https://lalescu.ro/liviu/fet/news.html

• Updated to Qt 6.5.1.
• Corrected a few English fields.
• Updated the Italian translation.
• Updated the Greek translation.

While here, pet linters.

PR: 271950
Reported by: uzsolt@uzsolt.hu (maintainer)