Fix binding loop in Desktop.qml for side panel height
This binding loop:
file:///home/nate/kde/usr/share/plasma/shells/org.kde.plasma.desktop/contents/views/Desktop.qml:146:19: QML Loader: Binding loop detected for property "height"
The loader for the side panel is attempting to calculate its height by taking into account margins from the item that it loads, which does not work because that item is not loaded yet.
Also, even if this did work, the net result would be to possibly cause the side panel to not take up the full height of the screen, which would look weird.
Let's fix this by making the height of the loader equal to the screen height, ignoring dialog margins.