popup: fix popup sizing when scroll enabled.

Summary:
Force immediate calculate on main_layout after sizing hints set.

@fix T6886

Test Plan: Elementary_test: popup -> select scrollable -> use popup examples.

Reviewers: committers, zmike, stephenmhouston, bu5hm4n, devilhorns

Reviewed By: committers, zmike, stephenmhouston

Subscribers: cedric

Tags: efl

Maniphest Tasks: T6886

Differential Revision: https://phab.enlightenment.org/D6509