Fix binding loop in ClipboardItemDelegate

Label has     verticalAlignment: lineCount > 1 ? Text.AlignTop :
Text.AlignVCenter

but in this delegate the height stretches to fit the text:
- height depends on verticalAlignment
- lineCount depends on height

creating a loop with this in the middle.

In this case we always want delegates in the middle, so we can just
override the superclass.

applets/clipboard/contents/ui/ClipboardItemDelegate.qml

@@ -102,6 +102,8 @@ PlasmaComponents.ListItem {
             width: parent.width
             height: undefined // unset PlasmaComponents.Label default height
             maximumLineCount: 3
+            verticalAlignment: Text.AlignVCenter
+
             text: {
                 var highlightFontTag = "<font color='" + theme.highlightColor + "'>%1</font>"