NB Muli Cursor -- Undo/Redo operation failure

[Yoyokrazy]

Re: #141673

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Undo operation only applied to 1 of 2 models. Fails rarely ❄️

• two cells, both with only `print("hello world")
• cursor on the first hello
• trigger cmd+d twice, selecting both
• backspace/delete (trigger deleteLeft)
• undo
• 🐛 only second cell is restored