Clean up Diffusion behaviors for inline edit suggestions

Summary: Ref T13513. For now, I'm not supporting inline edit suggestions in Diffusion, although it's likely not difficult to do so in the future. Clean up some of the code so that plain ol' inlines work the same way they did before.

Test Plan:

• Created, edited, reloaded, submitted inlines in Diffusion: familiar old behavior.
• Created, edited, reloaded, submitted inlines with suggestions in Differential: familiar new behavior.

Maniphest Tasks: T13513

Differential Revision: https://secure.phabricator.com/D21278