Remove redundant lockscreen shown check

Symptom:
USB dialog is displayed incompletely and cannot be scrolled under
lockscreen in multi-window mode.

Root cause:
When lockscreen is shown, the bounds returned by getLaunchBounds()
is null, updateOverrideConfiguration() will finally consider the task
as fullscreen, USB dialog is under lockscreen, not over lockscreen,
as a result, the height measured in ViewRootImpl's performTraversals()
will be incorrect.

Solution:
Remove the lockscreen shown check from getLaunchBounds() which is
originally added to fix app over lockscreen being cropped by docked
stack, and the following commit also fix the behavior of app over
lockscreen.

 https://android.googlesource.com/platform/frameworks/base/+/99732940809058fae558618399323c36b8a0e856

So that above check should be redundant code.

Bug: 31256862
Fixes: 36163229
Test: manual
Change-Id: Iac483f625d2f4b35388290eb78a97a4bd3bd0fe8