[flexiglass] Show bouncer when lockscreen is clicked on desktop

Use better suited way to detect situations where click-based
behavior is preferred over swipe-based behavior.

Test: manually verified that clicking on the background of the
lockscreen scene doesn't bring up the bouncer on phones, but does
on desktop
Flag: NONE this is a very simple change and the non-flexi codepath isn't
flag protected

Bug: 412922805
Bug: 433950243
Change-Id: I51fb1c87008a301db4a485735442d02b08e21df3