Skip checkAppWindowsReadyToShow for shell transition

It is used to handle allDrawn/mFreezingScreen/mOpeningApps.
(See ActivityRecord#checkAppWindowsReadyToShow)
All of them are not used by shell transition.

It may reduce requesting additional surface placement that
is triggered from FINISH_LAYOUT_REDO_ANIM.

Bug: 297493149
Test: CtsWindowManagerDeviceActivity
Change-Id: If4968ad8e9d896d79b6da30ead7122b2bb1e0855