[app/volume] Use property setter

app/qml/volume.qml

@@ -52,7 +52,7 @@ Kirigami.Page
 
                 Button {
                     icon.name: muted ? "player-volume-muted" : "player-volume"
-                    onClicked: pluginInterface.sendMuted(name, !muted)
+                    onClicked: muted = !muted
                 }
 
                 Slider {
@@ -60,7 +60,7 @@ Kirigami.Page
                     from: 0
                     value: volume
                     to: maxVolume
-                    onMoved: pluginInterface.sendVolume(name, value)
+                    onMoved: volume = value
                 }
             }
         }

interfaces/remotesinksmodel.cpp

@@ -164,7 +164,7 @@ QVariant RemoteSinksModel::data(const QModelIndex& index, int role) const
     }
 }
 
-bool RemoteSinksModel::setData(const QModelIndex &index, const QVariant &value, int role) 
+bool RemoteSinksModel::setData(const QModelIndex &index, const QVariant &value, int role)
 {
     if (!index.isValid()
         || index.row() < 0