elm_gen_common: fix typo in Struct variable documentation
elm_gen_common: fix typo in Struct variable documentation

Reviewers: Hermet, cedric

Reviewed By: cedric

Differential Revision: https://phab.enlightenment.org/D2634

Signed-off-by: Cedric BAIL <240633aa59d25638de9800ef43a88ad2e208d24d@osg.samsung.com>

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