Bug#1032412: Plymouth changed

[Gert van de Kraats]

At plymouth the computation of Window.GetWidth() and Window.GetHeight()
has changed 2 years ago. It now contains the sizes of the
largest screen i.s.o. the smallest screen.
See merge-request
https://gitlab.freedesktop.org/plymouth/plymouth/-/merge_requests/121 :
"use resolution of higher res monitor for window size" .