breezedecoration.cpp match newly introduced (5.23) upstream behavior

[DiabeticCrab]

The use of registerPlugin<Breeze::Button>(QStringLiteral("button")); in breezedecoration,cpp is deprecated and can be replaced with registerPlugin<Breeze::Button>();

Upstream patch: https://invent.kde.org/plasma/breeze/-/commit/79e32241c13d9ad3065c478f1e5870551b4a5284

Adapted for this repo: 0001-Merge-5.23-main-upstream-patch-and-fix-window-button.patch.txt

The part about fixing window-buttons-applet in the patch notes isn't correct anymore since the developer added a workaround to account for legacy behaviour for the time being. Moving forward, all decorations based on breeze should adapt this patch however (I think).

[kupiqu]

Thanks for letting me know. Could you please open a pull request?

[kupiqu]

Fixed with #99