Avoid monochrome icons in launcher and task panel

See 18d95dc927

containments/homescreen/package/contents/ui/launcher/Delegate.qml

@@ -117,6 +117,7 @@ ContainmentLayoutManager.ItemContainer {
                 Layout.minimumHeight: parent.height - root.reservedSpaceForLabel
                 Layout.preferredHeight: Layout.minimumHeight
 
+                usesPlasmaTheme: false
                 source: modelData ? modelData.ApplicationIconRole : ""
                 Behavior on scale {
                     NumberAnimation {

containments/taskpanel/package/contents/ui/Task.qml

@@ -95,6 +95,7 @@ Item {
                 anchors.centerIn: parent
                 width: Math.min(parent.width, parent.height) / 2
                 height: width
+                usesPlasmaTheme: false
                 source: model.decoration
             }
             PlasmaComponents.Label {