un-namespace some includes

Otherwise this repo fails to build against current KF6:

[ 25%] Building CXX object kcms/mouse/CMakeFiles/kapplymousetheme.dir/kapplymousetheme_autogen/mocs_compilation.cpp.o
/home/nate/kde/src/plasma-desktop/applets/taskmanager/plugin/backend.cpp:23:10: fatal error: KService/KApplicationTrader: No such file or directory
   23 | #include <KService/KApplicationTrader>
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.



[ 61%] Building CXX object kcms/touchpad/CMakeFiles/touchpad.dir/backends/x11/xrecordkeyboardmonitor.cpp.o
/home/nate/kde/src/plasma-desktop/kcms/mouse/kcm/configcontainer.cpp:12:10: fatal error: KWindowSystem/kwindowsystem.h: No such file or directory
   12 | #include <KWindowSystem/kwindowsystem.h>
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.



[ 69%] Building CXX object kcms/activities/CMakeFiles/kcm_activities.dir/kcm_activities_autogen/mocs_compilation.cpp.o
In file included from /home/nate/kde/build6/plasma-desktop/kcms/componentchooser/kcm_componentchooser_autogen/EWIEGA46WW/moc_componentchooser.cpp:10,
                 from /home/nate/kde/build6/plasma-desktop/kcms/componentchooser/kcm_componentchooser_autogen/mocs_compilation.cpp:3:
/home/nate/kde/build6/plasma-desktop/kcms/componentchooser/kcm_componentchooser_autogen/EWIEGA46WW/../../../../../../src/plasma-desktop/kcms/componentchooser/componentchooser.h:10:10: fatal error: KI18n/KLocalizedString: No such file or directory
   10 | #include <KI18n/KLocalizedString>
      |          ^~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.

@nicolasfella