R1:01fba3432707

Give `<hr />` in remarkup `clear: both`

Summary: Ref T10110.

Test Plan:
Before:

{F1058545}

After:

{F1058546}

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10110

Differential Revision: https://secure.phabricator.com/D14984