Don't attempt to stash new section edits

The parser output of edits produced via the 'new section' interface varies on
both the edit body and the edit summary (since it determines the new section's
name). So there isn't an early point in the edit process where we can start
computing the edit output. We have to wait for the user to be completely
done, by which point edit-stashing provides no advantage.

Change-Id: Ida461e08189b75c5a508628d11dc929a6138814a