Bind list delegate widths using id, not parent

parent is invalid in the context of a list delegate, which causes a
console warning.

discover/qml/ReviewsPage.qml

@@ -78,7 +78,7 @@ Kirigami.OverlaySheet {
         cacheBuffer: Math.max(0, contentHeight)
 
         delegate: ReviewDelegate {
-            width: parent.width
+            width: reviewsView.width
             separator: index != ListView.view.count-1
             onMarkUseful: page.model.markUseful(index, useful)
         }

libdiscover/backends/SnapBackend/qml/ChannelsButton.qml

@@ -28,7 +28,7 @@ Button
             }
             model: resource.channels(root).channels
             delegate: RowLayout {
-                width: parent.width
+                width: view.width
                 readonly property bool current: resource.channel === modelData.name
                 Label {
                     Layout.fillWidth: true

libdiscover/backends/SnapBackend/qml/PermissionsButton.qml

@@ -28,7 +28,7 @@ Button
             model: resource.plugs(root)
             delegate: CheckDelegate {
                 id: delegate
-                width: parent.width
+                width: view.width
                 text: model.display
                 checked: model.checked
                 onClicked: {