This makes sure all of the supported protocols have a chance of working.
Since nua_set_params does not update NUTAG_URL (carefully rechecking the docs
verifies this), it is safe to remove the code in update_nua().
However, this means that we will have to recreate the nua stack,
which incidentally is currently being worked on:
https://gitlab.gnome.org/GNOME/calls/-/merge_requests/402