Bump plasma-wayland-protocols dependency to 1.2.1
The 1.2.0 release of plasma-wayland-protocols has wrong project version in CMakeLists.txt, which causes problems during packaging KWayland. This issue is addressed in 1.2.1
This change bumps plasma-wayland-protocols dependency so packagers have a better idea what p-w-p is needed in order to build kwayland 5.81.