Fix trend icon sizes on the statistics page

src/app/StatisticsDelegate.qml

@@ -22,8 +22,8 @@ RowLayout {
     Kirigami.Icon {
         source: root.statItem.trend == StatisticsItem.TrendUp ? "go-up-symbolic" : root.statItem.trend == StatisticsItem.TrendDown ? "go-down-symbolic" : "go-next-symbolic"
         color: root.statItem.trend == StatisticsItem.TrendUp ? Kirigami.Theme.negativeTextColor : root.statItem.trend == StatisticsItem.TrendDown ? Kirigami.Theme.positiveTextColor : Kirigami.Theme.textColor
-        width: height
-        height: Kirigami.Units.gridUnit
+        Layout.preferredWidth: Kirigami.Units.gridUnit
+        Layout.preferredHeight: Kirigami.Units.gridUnit
         visible: root.statItem.trend != StatisticsItem.TrendUnknown
     }