[applets/batterymonitor] CompactRepresentation: Fix ReferenceError

Fixes the following error:

    /usr/share/plasma/plasmoids/org.kde.plasma.battery/contents/ui/CompactRepresentation.qml:74:
    ReferenceError: batteryLabel is not defined

batteryLabel does not exist ever since commit
27ac0b7608 back in 2016, so an attempt to
calculate some icon's height based on its size was bound to fail.

applets/batterymonitor/package/contents/ui/CompactRepresentation.qml

@@ -71,7 +71,7 @@ MouseArea {
                     id: batteryIcon
 
                     anchors.centerIn: parent
-                    height: root.isConstrained ? batteryContainer.iconSize : batteryContainer.iconSize - batteryLabel.height
+                    height: batteryContainer.iconSize
                     width: height
 
                     hasBattery: batteryContainer.hasBattery