Set saner widths for Placeholder messages so their text doesn't overflow

See D29692

applets/clipboard/contents/ui/Menu.qml

@@ -59,9 +59,7 @@ PlasmaExtras.ScrollArea {
             id: emptyHint
 
             anchors.centerIn: parent
-            anchors.left: parent.left
-            anchors.right: parent.right
-            anchors.margins: units.largeSpacing
+            width: parent.width - (units.largeSpacing * 4)
 
             visible: menuListView.count === 0
             text: i18n("Clipboard is empty")

applets/notifications/package/contents/ui/FullRepresentation.qml

@@ -586,9 +586,7 @@ PlasmaComponents3.Page {
 
                 Kirigami.PlaceholderMessage {
                     anchors.centerIn: parent
-                    anchors.left: parent.left
-                    anchors.right: parent.right
-                    anchors.margins: units.largeSpacing
+                    width: parent.width - (units.largeSpacing * 4)
 
                     text: i18n("No unread notifications")
                     visible: list.count === 0 && NotificationManager.Server.valid