These strings were recently found to have been confusing to the translators. Improvements are:
- Pulling the (untranslated) error message out of the message sentence. We really want the error message to be at the end so we'll force the translators to translate it as a prefix.
- Remove extra spaces at the end.
- Remove Python logic from within the i18nc call, since gettext doesn't understand that.
Contributes to issue CURA-5741.
