Separator: Add namespace for enum access
It doesn't seem to work on Qt dev branch anything namespace prefix anymore:
file:///usr/local/qt-dev/qml/org/kde/kirigami/Separator.qml:47: TypeError: Cannot read property 'Light' of undefined
file:///usr/local/qt-dev/qml/org/kde/kirigami/Separator.qml:41: TypeError: Cannot read property 'Normal' of undefined