SSH config UI: use "delete" consistently, avoid Yes/No buttons
"Delete" instead of "Remove" makes it more obvious the data is gone afterwards, not just removed from a list.
Also use KMessageBox::warningYesNo instead of the helper method KMessageBox::messageBox. And fix missing i18n markup of menu entry.
Yes/No buttons in dialogs are discouraged (not only) by KDE HIG in favour of actions terms.