Apple remarkup-code padding to child spans as well.

Summary: Fixes T6440. The issue is when a nested span appears, we don't apply the spacing.

Test Plan: Test a new diff in my sandbox that exhibits the issue. Ensure spacing now aligns.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T6440

Differential Revision: https://secure.phabricator.com/D10768