api: remove required flag of gatewayid in CreateStaticRouteCmd (#12786)

Author: weizhouapache

api/src/main/java/org/apache/cloudstack/api/command/user/vpc/CreateStaticRouteCmd.java

@@ -46,7 +46,6 @@ public class CreateStaticRouteCmd extends BaseAsyncCreateCmd {
     @Parameter(name = ApiConstants.GATEWAY_ID,
                type = CommandType.UUID,
                entityType = PrivateGatewayResponse.class,
-               required = true,
                description = "The gateway ID we are creating static route for. Mutually exclusive with the nexthop parameter")
     private Long gatewayId;