Clean up outdated path of sleep token for swapping display

Since commit 20e51039 was enabled from previous release, there no longer
has activity lifecycle changes when folding or unfolding the device.

The deferring of activity-stop in commit 0687f9d3 can be removed because
the case of isSwappingDisplay=true for updateScreenOffSleepToken is gone.

Bug: 163976519
Bug: 303241079
Flag: EXEMPT remove launched flag
Test: atest PhoneWindowManagerTests#testScreenTurnedOff

Change-Id: Ia991eab37793c159c7a1afb1276cf82ad6ad0462