[Redesign] More space for remarkup-list

Summary: Ref T8099, Feel like this got reverted somewhere, but list elements should have more space (for lists of objects).

Test Plan: Review a list of objects.

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin

Maniphest Tasks: T8099

Differential Revision: https://secure.phabricator.com/D13452