It seems that the translation was never done: viewtopic.php?f=66&t=659365&hilit=georgian
You will have to translate everything in the language folder and also create some images for the interface buttons.
If you have a test installation (which I recommend), you can edit the files in Admin -> System -> Language packs.
Sadly, they only accept 100% translations and you will need to translate not only the user interface, but the full admin interface as well before you can get an official release. It is doable though if you keep at it long enough, and in the meantime you can always upload a zip file here.
More info: https://www.phpbb.com/languages/apply.php