lockscreen: prevent immediate prompting for the password
As of Qt 6.8.2, the fix for QTBUG-127122 causes a positionChanged event to be emitted when handling QEvent::HoverEnter.
The lockscreen creates a full screen MouseArea on every connected screen, one of which will cover the current position of the mouse pointer. This causes QEvent::HoverEnter and then the positionChanged event to be raised immediately. The mouse position did not change. Ignore the spurious (first) positionChanged event, show the password UI as usual in response to further events.