Fix qdbusxml2cpp crash due to annotation type.

When building in qt6 mode I get an error from qdbusxml2cpp which boils
down to:

    [103/164] Generating dbusmenuadaptor.cpp, dbusmenuadaptor.h
    FAILED: src/dbusmenuadaptor.cpp src/dbusmenuadaptor.h dbusmenuadaptor.cpp dbusmenuadaptor.h
    /home/kde-svn/qt6/bin/qdbusxml2cpp -m -a dbusmenuadaptor -i src/libdbusmenu-qt/dbusmenuexporterdbus_p.h -l DBusMenuExporterDBus src/libdbusmenu-qt/com.canonical.dbusmenu.xml
    src/libdbusmenu-qt/com.canonical.dbusmenu.xml:321:5: warning: Unknown element 'd' while checking for signal arguments
    src/libdbusmenu-qt/com.canonical.dbusmenu.xml:327:68: error: Invalid Interface specification
    src/libdbusmenu-qt/com.canonical.dbusmenu.xml:327:68: error: XML error: Unexpected '<'.

The line in question is (erroring on "<type">):
    <annotation name="org.qtproject.QtDBus.QtTypeName.Out0" value="<type>"/>

I suspect this is due to upcoming Qt 6.7's qdbusxml2cpp getting stricter
because this seemingly must have worked earlier, but I just updated Qt 6
today and instantly ran into this.  The specific problem seems to be
that "<type>" is meant to be filled in with an actual C++ type -- if I
remove the annotation entirely then qdbusxml2cpp instead tells me an
annotation is missing and the error message suggests to add that line.

In this case it wasn't meant to be taken entirely literally, I suspect,
but to have <type> replaced with an appropriate type.  I don't know what
the types are supposed to be, but there are 2 nearby annotations flagged
as input types that seem to be the right shape.

So my fix for this is to remove the annotation entirely and replace the
2 existing annotations which appear to be improperly flagged as input
types as output types instead.  I suspect this was a bug from when these
annotations were first introduced since signals cannot receive input.

This change makes qdbusxml2cpp happy and lets knotifications complete
building.  But note that I haven't managed to test yet, I'm still in the
midst of setting up my first Qt6/KF6-based Plasma environment.