efl_canvas_animation_group: remove implicit children behaviour

efl_canvas_animation_group: remove implicit children behaviour

you could set the duration of the group to all children, however, the
default behaviour was to not do that. This is however a bit probeblatic,
and needs to be more expclicit. If this is needed again, then this can
be reintroduced, however, not in this form.

ref T8437
Depends on D10798

Reviewed-by: Xavi Artigas <xavierartigas@yahoo.es>
Differential Revision: https://phab.enlightenment.org/D10799