Codechange: Remove CargoSpec::multipliertowngrowth which is unused (#9701)

This is set by cargo property 19.
This property is only implemented in TTDPatch.

src/cargotype.h

@@ -66,7 +66,6 @@ struct CargoSpec {
 
 	bool is_freight;                 ///< Cargo type is considered to be freight (affects train freight multiplier).
 	TownEffect town_effect;          ///< The effect that delivering this cargo type has on towns. Also affects destination of subsidies.
-	uint16 multipliertowngrowth;     ///< Size of the effect.
 	uint8 callback_mask;             ///< Bitmask of cargo callbacks that have to be called
 
 	StringID name;                   ///< Name of this type of cargo.

src/newgrf.cpp

@@ -3019,7 +3019,7 @@ static ChangeInfoResult CargoChangeInfo(uint cid, int numinfo, int prop, ByteRea
 			}
 
 			case 0x19: // Town growth coefficient
-				cs->multipliertowngrowth = buf->ReadWord();
+				buf->ReadWord();
 				break;
 
 			case 0x1A: // Bitmask of callbacks to use

src/table/cargo_const.h

@@ -44,7 +44,7 @@
  * @param classes      Classes of this cargo type. @see CargoClass
  */
 #define MK(bt, label, colour, weight, mult, ip, td1, td2, freight, te, str_plural, str_singular, str_volume, classes) \
-		{bt, label, colour, colour, weight, mult, ip, {td1, td2}, freight, te, 0, 0, \
+		{bt, label, colour, colour, weight, mult, ip, {td1, td2}, freight, te, 0, \
 		MK_STR_CARGO_PLURAL(str_plural), MK_STR_CARGO_SINGULAR(str_singular), str_volume, MK_STR_QUANTITY(str_plural), MK_STR_ABBREV(str_plural), \
 		MK_SPRITE(str_plural), classes, nullptr, nullptr, 0}