Codechange: Cargo filters no longer take an index. (#11582)

Update naming of functions to reflect that parameter is now a cargoid.

src/vehicle_gui_base.h

@@ -121,7 +121,7 @@ struct BaseVehicleListWindow : public Window {
 	void UpdateVehicleGroupBy(GroupBy group_by);
 	void SortVehicleList();
 	void BuildVehicleList();
-	void SetCargoFilterIndex(byte index);
+	void SetCargoFilter(byte index);
 	void SetCargoFilterArray();
 	void FilterVehicleList();
 	StringID GetCargoFilterLabel(CargoID cid) const;