Replacing cell outputs should hard-reload

[krassowski]

In #360 I added:

jupyter_ydoc/jupyter_ydoc/ynotebook.py

Lines 348 to 351 in 87919c6

	if key == "output" and value:
	# outputs require complex handling - some have Text type nested;
	# for now skip creating them; clearing all outputs is fine
	return False

but it should have been outputs with an s.