elm_conform: remove smart_callback when it is removed.
elm_conform: remove smart_callback when it is removed.

The owner of the smart_callbacks is window. so even if the conformant
is deleted, they aren't removed. It can make some problems.

@fix

FlorentRevest/Elementary,rvandegrift/elementary,tasn/elementary,FlorentRevest/Elementary,FlorentRevest/Elementary,rvandegrift/elementary,tasn/elementary,tasn/elementary,rvandegrift/elementary,tasn/elementary,FlorentRevest/Elementary,rvandegrift/elementary,tasn/elementary