gtk-demo: Make style apply in the file browser

Commit 5afe6f7825 claims to make this demo
'look good', but it failed to actually make its
css apply. Now it really looks good.

demos/gtk-demo/listview_filebrowser.css

@@ -1,11 +1,11 @@
-list.viewswitcher {
+listview.viewswitcher {
   border: 1px solid gray;
 }
 
-list.viewswitcher > row {
+listview.viewswitcher > row {
   padding: 5px;
 }
 
-list.viewswitcher row:selected {
+listview.viewswitcher row:selected {
   background: gray;
 }