atspi: remove useless "GetDefaultAttributeSet" method
atspi: remove useless "GetDefaultAttributeSet" method

This method exists in atspi spec, however is not implemented
in libatspi library. Drop it for now as it seems useless.

tasn/elementary,tasn/elementary,rvandegrift/elementary,tasn/elementary,rvandegrift/elementary,tasn/elementary,rvandegrift/elementary,rvandegrift/elementary,tasn/elementary