greeter: dialog box automatic display switching workaround

System: elementaryOS 5.1.5
Concerned package: `wingpanel`, `pantheon-greeter` (I think)
Possible Impact: Low/Wishlist

Expected behaviour:
The login screen dialog box will automatically switch to the desktop that the mouse cursor is on.

Workaround:
If the mouse leaves the display through `wingpanel` on the top right or top left of the display, the login dialog will no longer switch to that display, no matter how long the cursor stays on that display. If the mouse cursor returns to original display and leaves through anywhere other than the indicators, the behaviour returns to normal.

This only happens on the display with `wingpanel` on it (i.e. if the display does not have `wingpanel` on it, this will not happen).