Temporarily always animate at 60fps

Libcosmic needs to correctly expose a subscription to the
display's refresh rate.

src/timeline.rs

@@ -575,7 +575,7 @@ impl Timeline {
                     || (track.0.end >= now.unwrap() && track.0.pause.is_playing())
             })
         {
-            cosmic::iced_runtime::window::frames()
+            cosmic::iced::time::every(Duration::from_millis(16)) // ~60FPS
         } else {
             Subscription::none()
         }