Editor: Moving autobulleted line down causes duplicate `*` character

[roundhill]

To repro:

1. Enter * start a line like this on iOS
2. Then put your cursor before the *, and press enter
3. it becomes * * start a line like this on iOS

I also run into this when I'm trying to copy and paste lists between each other, it's hard to put something in the middle.

[bummytime]