Partially revert "Show Progress button also when syncing to device"

This reverts commit b5b86da519 on the
part of syncui.py.

Remove start_cb, show the progress button on main.py.

src/gpodder/gtkui/main.py

@@ -4161,15 +4161,13 @@ class gPodder(BuilderWidget, dbus.service.Object):
                 gPodderEpisodeSelector,
                 self.mount_volume_for_file)
 
-        def start_cb():
-            self.transfer_revealer.set_reveal_child(True)
-
         def done_cb():
             self.set_download_list_state(gPodderSyncUI.DL_ONEOFF)
             util.idle_add(self.transfer_revealer.set_reveal_child, False)
 
+        self.transfer_revealer.set_reveal_child(True)
         self.sync_ui.on_synchronize_episodes(self.channels, episodes, force_played,
-                                             done_cb, start_cb)
+                                             done_cb)
 
     def on_extension_enabled(self, extension):
         if getattr(extension, 'on_ui_object_available', None) is not None:

src/gpodder/syncui.py

@@ -96,7 +96,7 @@ class gPodderSyncUI(object):
         message = _('Please check logs and the settings in the preferences dialog.')
         self.notification(message, title, important=True)
 
-    def on_synchronize_episodes(self, channels, episodes=None, force_played=True, done_callback=None, start_callback=None):
+    def on_synchronize_episodes(self, channels, episodes=None, force_played=True, done_callback=None):
         device = sync.open_device(self)
 
         if device is None:
@@ -114,9 +114,6 @@ class gPodderSyncUI(object):
             # Only set if device is configured and opened successfully
             self.device = device
 
-        if start_callback is not None:
-            start_callback()
-
         if episodes is None:
             force_played = False
             episodes = self._filter_sync_episodes(channels)