efl_ui_widget: remove "moved" event
This "moved" event is only used by elm_gengrid now.
And it's not something common for all widget classes,
because the event is giving notification when the legacy
item is reordered.
Test Plan: elementary_test "GenGrid"
Reviewers: bu5hm4n, YOhoho, Jaehyun_Cho
Reviewed By: bu5hm4n, YOhoho
Maniphest Tasks: T7553
Differential Revision: https://phab.enlightenment.org/D8005