Fix: only count distance traveled in vehicles for cargo payment (#11283)

No longer you can utilize the free (and instant) labour of station
workers, transporting your cargo from one part of the station to
the other. No more!

Based on patch by dP.

src/saveload/saveload.h

@@ -360,6 +360,7 @@ enum SaveLoadVersion : uint16_t {
 	SLV_PERIODS_IN_TRANSIT_RENAME,          ///< 316  PR#11112 Rename days in transit to (cargo) periods in transit.
 	SLV_NEWGRF_LAST_SERVICE,                ///< 317  PR#11124 Added stable date_of_last_service to avoid NewGRF trouble.
 	SLV_REMOVE_LOADED_AT_XY,                ///< 318  PR#11276 Remove loaded_at_xy variable from CargoPacket.
+	SLV_CARGO_TRAVELLED,                    ///< 319  PR#11283 CargoPacket now tracks how far it travelled inside a vehicle.
 
 	SL_MAX_VERSION,                         ///< Highest possible saveload version
 };