No need to use getExpandedBubble for singleTaskDisplayDrawn/Empty callbacks

getExpandedBubble checks if the shade is expanded or not and returns
null if the shade is expanded, we don't care about that for the display
drawn callbacks.

Test: manual, have a bubble notification on lockscreen, tap it, note
      that the bubble is expanded & visible after going through lockscreen
Bug: 138461119
Change-Id: I00dff7cd3301db6a2613a947015ac0408b545202