- The modal content of the popup snippet had a maximum height of 100%
because of a global rule on modals. But, here, the scrollable element
is not the modal so we dont want this rule.

- For the popup to be scrolled correctly we also had to remove the
rule that adds a fixed 100% height on modal-dialog and we added a
min-height of 100% to correctly display the popup in the middle
position.

Part of https://github.com/odoo/odoo/pull/61998
task-2312878