fileselector_button: Added missing description about focus signals.
fileselector_button: Added missing description about focus signals.

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