fix: Revert TooltipHideEvent to MouseOutEvent (#3909)

Alternative approach to #3907, which selectively reverts only one line
from #3781 in order to mitigate #3893.

packages/vega-scenegraph/src/util/events.js

@@ -50,6 +50,6 @@ export const Events = [
 
 export const TooltipShowEvent = PointerMoveEvent;
 
-export const TooltipHideEvent = PointerOutEvent;
+export const TooltipHideEvent = MouseOutEvent;
 
 export const HrefEvent = ClickEvent;