These haven't been updated since their addition, so this updates the list that controls which qt base translations are bundled with the macOS binary, to all the languages that are available with qt 5.9.8. This could probably be improved in some way, however qt updates are infrequent, and I didn't want to spend any more time looking at this. Also given that no-one seems to have noticed and/or reported this it wouldn't seem high-priority.
Backport of core PR19059.