Update some Ukrainian translations

[olexandr-konovalov]

This improves #565 now when I better understand how they are used...

Did it with

library(potools)
potools::po_extract()
potools::po_update()
potools::po_compile()

and committed three updated files. Not sure if .pot is needed, but allowing edits by maintainers - will hugely appreciate merging it quickly for the training I run on Monday January 15th. Thank you!!!