don't accept active focus on tab

this was actually breaking keyboard navigation
see https://bugreports.qt.io/browse/QTBUG-63176
for our use case in pasmashell, it's better to just
rely on focus of the internal items or of the
ListView
reviewed-by: davidedmundson

src/declarativeimports/plasmaextracomponents/qml/ScrollArea.qml

@@ -36,6 +36,7 @@ QtQuickControls.ScrollView {
 
     style: Styles.ScrollViewStyle{}
     frameVisible: true
+    activeFocusOnTab: false
 
     //START HACK
     //The following is a workaround for QTBUG-17051