Fix find_package(KF6Kirigami2) calls
CMake doesn't like it when there's no Version file. Also, while we don't have a main Kirigami library anymore, we can include KirigamiPlatform as a dependency for the main thing.
CMake doesn't like it when there's no Version file. Also, while we don't have a main Kirigami library anymore, we can include KirigamiPlatform as a dependency for the main thing.