effects/Overview: Use SearchField from PlasmaExtras

(cherry picked from commit 4eefd27f)

src/effects/overview/qml/ScreenView.qml

@@ -198,7 +198,7 @@ FocusScope {
                 width: parent.width
                 height: searchField.height + 2 * PlasmaCore.Units.largeSpacing
 
-                PC3.TextField {
+                PlasmaExtras.SearchField {
                     id: searchField
                     anchors.centerIn: parent
                     width: Math.min(parent.width, 20 * PlasmaCore.Units.gridUnit)