Fix translated text

Summary:
`i18n` doesn't work before QCoreApplication is created, hence statically initialized text is not translated.

Related: D12626

Reviewers: ngraham, #spectacle, broulik, #localization, yurchor

Reviewed By: ngraham, #spectacle, yurchor

Subscribers: pino, yurchor, broulik, ngraham

Tags: #spectacle

Differential Revision: https://phabricator.kde.org/D17654