When a typewriter mode is active, changing the document string scrolls to bottom

It's not unusual for a NSTextView to place the insertion point (`selectedRange`) at the end of the document when you set its `string` to a new value. Usually, it doesn't scroll down there, though. Depending on the use case, this might not be desirable.

I figure this is due to the `fixInsertionPointPosition()` call which is there to do just that: re-set the `selectedRange` to make the view scroll and/or `forceLayoutWithNewInsets()`.