Revert logic to calculate StackEndHeight

This partially reverts the logic to compute the stackEndHeight, as it doesn't make the shelf stick at the bottom when scrolling notifications. This might reintroduce the bug of trimmed notifications on lockscreen, that will be addressed in another cl.

Bug: 227733494
Bug: 214504318
Fixes: 226054279
Test: Test: atest ShelfInvisibleWithLowNotifications && atest ShelfVisibleAtTheBottom
Change-Id: I20286eb961d46439a0d80980c085a41b93241cb8
1 file changed