Remove unused code

- The old character select scene, which was never shown but loaded
  every character image at startup
- Unused SyncResponse and ProgressResponse classes
- Playlist.set_last_played_answered and select/local-loading code in
  the new character select, none of which were called
- Settings.delete_player_children, identical to delete_children
- An unused variable holding a local file path

Settings.gd

@@ -36,8 +36,3 @@ func delete_children(node: Node) -> void:
 	for n: Node in node.get_children():
 		node.remove_child(n)
 		n.queue_free()
-
-func delete_player_children(node: Node) -> void:
-	for n: Node in node.get_children():
-		node.remove_child(n)
-		n.queue_free()