Drop functions which rely on PlasmaWindow::internalId()
While that returns a WinId, those are from the compositor and not related to the internal WinIds from the calling application itself. Most uses of KWindowSystem rely on that though, and so acted on a random other window instead.
This code seems to be a case of "never worked" to me, so dropping it shouldn't do much (or any) harm. I didn't discover any issues while playing around with this applied. It might even qualify for backporting to stable branches?
openQA seems happy now: https://openqa.opensuse.org/tests/1725330 vs. before: https://openqa.opensuse.org/tests/1724224