Select <td> padding for inlines more surgically

Summary:
Fixes T11225. The primary issue here is that this rule is bleeding down too far. It appears that it's only intended to put space around the inline as a whole.

Spacing still isn't perfect since a few other rules are bleeding, but it feels reasonable now instead of being clearly broken.

Test Plan:

• Added "background: red;" to figure out what was being affected.
• Before:

{F1704081}

• After:

{F1704084}

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T11225

Differential Revision: https://secure.phabricator.com/D16184