deskutils/fet: update to 6.9.3

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

• Updated to Qt 6.5.2.
• The activities import/export from/to CSV files will now process correctly the individually modified subactivities. The different components will be separated by the | symbol.
• Corrected a few English fields
• Updated the Greek translation

PR: 272683
Reported by: uzsolt@uzsolt.hu (maintainer)