Fix scrolling on the EntryDetails page

Summary:
For ScrollablePage to be able to scroll, the scrollable content must
be the last Item on the page.

BUG:418191

Reviewers: ngraham, Frameworks, Plasma, hexchain

Reviewed By: hexchain

Subscribers: kde-frameworks-devel

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D27696