devel/kf5-knewstuff: cleanup dependencies

TextWidgets was removed in [1] and Sonnet added as an option in [2].

[1] https://invent.kde.org/frameworks/knewstuff/-/commit/68b1523413a69c5fa02f708025085c8fdc69e8ce
[2] https://invent.kde.org/frameworks/knewstuff/-/commit/88cb903970ea95119c105823f01c7f7ee2cabf09