Redundant parameter in SaveFiles() method from FileChooser portal

[grulja]

In xdp_portal_save_files() users might pass current_name parameter, but this one is not mentioned in xdg-desktop-portal documentation and doesn't seem to make sense in this call as you are saving multiple files at once.

[grulja]

This probably cannot be solved (removed) at this moment as it would break API for those using it already. On the other hand I don't expect many apps using it yet, especially the xdp_portal_save_files() function so perhaps it's safe to remove it in this early stage? It probably won't cause any harm having it there, it's just it might be confusing for someone.

[hadess]

@mjog wrote the SaveFiles functionality IIRC.