kcm/rules: Port away from Kirigami.AbstractListItem

It's being removed for KF6 and ItemDelegate works fine here.

src/kcms/rules/ui/RuleItemDelegate.qml

@@ -10,7 +10,7 @@ import QtQuick.Controls as QQC2
 import org.kde.kirigami 2.10 as Kirigami
 import org.kde.kcmutils as KCM
 
-Kirigami.AbstractListItem {
+QQC2.ItemDelegate {
     id: ruleDelegate
 
     property bool ruleEnabled: model.enabled

src/kcms/rules/ui/RulesEditor.qml

@@ -192,7 +192,7 @@ KCM.ScrollViewKCM {
                 }
             }
 
-            delegate: Kirigami.AbstractListItem {
+            delegate: QQC2.ItemDelegate {
                 id: propertyDelegate
                 highlighted: false
                 width: ListView.view.width