web client: update the plr_flag_id enum.
web client: update the plr_flag_id enum.

The player flag "ScenarioReserved" was added in Freeciv r31064.

adaxi/freeciv-web,adaxi/freeciv-web,adaxi/freeciv-web,andreasrosdal/freeciv-web,andreasrosdal/freeciv-web,andreasrosdal/freeciv-web,adaxi/freeciv-web,andreasrosdal/freeciv-web,adaxi/freeciv-web,andreasrosdal/freeciv-web