fix the parameter order for the "is_writer" function call.

[derrick-yang]

The is_writer funtion call has a incorrect parameter order.
Since is_writer is defined as
fn is_writer(self: @T, component: felt252, system: felt252) -> bool;

The call in world.cairo is IWorld::is_writer(@self, caller_system(@self), component)

[tarrencev]

ah thank you! we should add a test here too