Mark text as not translatable in UI files

> If this is the case, we might want to update a few more ui files and mark text as not translatable to minimize translation effort. What do you think?

Probably worth a separate issue for 3.10.0 but yes.

For now, this can be left as is, as it's not used.

_Originally posted by @pljones in https://github.com/jamulussoftware/jamulus/pull/2835#discussion_r964166516_

Start by reviewing the discussion referenced from pull request #2835 and locating the UI files that contain the text in scope. Confirm which strings should be marked as not translatable and check the surrounding translation handling before making changes. Done means the intended UI text is excluded from translation without affecting other strings.

Written by the indexing model from the issue text.