### What?
Ensure the Rich Text field is read-only when viewing a locked document.
### Why?
When opening a locked doc in read-only mode, the Rich Text field could
still appear editable. This is inconsistent with other fields and allows
users to try typing into a locked document.
### How?
- Pass `readOnly={isTrashedDoc || isLocked}` into `buildFormState` in
the edit view renderer.